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No.  1902:  January  5,  1919 


On  a New  Exogyra  from  the  Del  Rio  Clay 
and  Some  Observations  on  the  Evolution 
of  Exogyra  in  the  Texas  Cretaceous 


GEOLOGY 


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University  of  Texas  Bulletin 

No.  1902:  January  5,  1919 

On  a New  Exogyra  from  the  Del  Rio  Clay 
and  Some  Observations  on  the  Evolution 
of  Exogyra  in  the  Texas  Cretaceous 


BY 


Emil  Bose 


Bureau  of  Economic  Geology  and  Technology 
Division  of  Economic  Geology 

J.  A.  Udden,  Director  of  the  Bureau  and  Head  of  the  Division 


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to  the  preservation  of  a free  govern- 
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only  dictator  that  freemen  acknowl- 
edge and  the  only  security  that  free- 
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>D  tO 


ON  A NEW  EXOGYRA  FROM  THE  DEL  RIO  CLAY 
AND  SOME  OBSERVATIONS  ON  THE  EVOLUTION 
OF  EXOGYRA  IN  THE  TEXAS  CRETACEOUS1 

By  Emil  Bose 


Nearly  twenty  years  ago  attempts  were  made  to  subdivide 
the  Texas  Cretaceous,  basing  stratigraphical  zones  on  the 
occurrence  of  oysters,  especially  Gryphaeas  and  Exogyras. 
That  such  a subdivision  must  be  doomed  to  failure  will  be 
evident  to  any  paleontologist  on  account  of  the  extreme 
variability  of  oysters,  Exogyra  included.  But  these  at- 
tempts are  interesting,  in  so  far  as  they  showed  that  Ex- 
ogyras occur  in  most  of  the  Cretaceous  beds  of  Texas  and 
that  all  these  may  be  related  to  each  other.  Exogyras  occur 
practically  from  the  lowest  stratum  of  the  Trinity  form- 
ation, which  corresponds  to  the  Aptian,  to  the  highest  Cre- 
taceous, the  Navarro  beds;  which  in  their  upper  part,  the 
higher  Escondido  beds,  certainly  represent  the  Maestrich- 
tian. 

In  order  to  show  the  evolution  of  Exogyra  in  the  Texas 
Cretaceous  a thorough  collection  of  specimens  of  this  genus 
in  the  different  beds  and  a redescription  of  the  known 
species  would  be  absolutely  necessary;  first,  because  many 
forms  are  still  undescribed;  and  second,  because  in  most 
of  the  described  species  the  development  from  the  smallest 
to  the  mature  individuals  has  not  been  sufficiently  taken 
into  account.  The  very  small  specimens  are  often  the  most 
important  ones,  because  their  ornamentation  is  frequently 
Qiuite  different  from  that  of  the  full  grown  individuals  and 
demonstrates  from  which  forms  in  lower  beds  the  species 
has  branched  off.  Often  the  ornamentation  on  the  very 
first  part  of  the  beak  of  mature  specimens  shows  also  this 
original  ornamentation,  but  generally  the  beak  has  been 
corroded  by  the  movement  of  the  shell  in  the  water  or  by 
the  grinding  effect  of  sand  in  currents.  In  these  cases  the 
beak  will  appear  smooth,  although  the  younger  specimens 
show  a decided  ornamentation.  In  Exogyra  the  evolution 


4 


1The  manuscript  for  this  paper  was  submitted  in  June,  1919: 
the  bulletin  was  issued  in  September,  1919.  (Ed.) 


4 


University  of  Texas  Bulletin 


of  the  beak  is  of  an  importance  similar  to  that  of  the  suture 
and  the  smaller  whorls  in  the  ammonites. 

More  than  twelve  years  ago,  when  I described  the  fauna 
of  the  Cerro  de  Muleros  near  Ciudad  Juarez,  Chihuahua, 
Mexico,  I felt  convinced  that  most  of  the  Texas  Exogyras 
had  developed  from  a common  tribe,  but  at  that  time  I did 
not  have  enough  material  and  there  seemed  to  exist  serious 
gaps  which  in  part  have  been  filled  since  that  date.  One 
of  them  especially  was  between  the  Vraconnian  and  the 
highest  Cenomanian;  or,  using  local  terms,  between  the 
uppermost  Edwards  limestone  and  the  Buda  limestone.  This 
latter  one  has  been  recently  filled  through  a discovery  made 
by  Mr.  W.  R.  Cartledge,  who  found  a new  Exogyra  in  the 
upper  part  of  the  Del  Rio  beds  in  the  region  near  the  quick- 
silver deposits  of  the  Terlingua  district;  a species  which 
will  be  described  farther  on. 

I do  not  propose  to  prove  that  the  evolution  of  the  Texan 
Exogyras  was  entirely  continuous,  because  my  material  is 
still  very  incomplete;  but  I wish  to  open  a road  for  some- 
body else  who  may  want  to  demonstrate  in  what  manner 
Exogyra  developed  in  Texas  during  the  Cretaceous.  It 
will  probably  be  found  that  such  an  evolution  existed  and 
was  at  least  partly  parallel  to  the  development  of  this  genus 
in  southern  Europe  and  northern  Africa;  possibly  in  the 
later  stages  also  in  Asia. 

Thus  the  content  of  the  following  paper  will  be  merely  a 
sketch,  but  it  may  point  out  a way  for  a monographicai 
description  of  the  Cretaceous  species  of  Exogyra  in  Texas.’ 

The  oldest  species  of  Exogyra  in  the  Texas  Cretaceous 
seemingly  occurs  in  the  lower  part  of  the  Trinity  formation, 
the  Basement  sands  or  Travis  Peak  formation  of  Travis 
County.  This  species  has  been  described,  although  net  fig- 
ured, by  Cragin1  as  Exogyra  Hilli.  He  asserts  that  it  has 
also  been  found  in  Arkansas,  where  it  was  described  by 
R.  T.  Hill.2  It  is  a small  form  somewhat  similar  in  out- 


1F.  W.  Cragin,  A contribution  to  the  invert.  Paleontol.  of  the  Texas 
Cretaceous.  4th  An.  Rep.  Geol.  Surv.  Texas,  1893,  p.  186. 

2R.  T.  Hill,  The  Mesozoic  geology  of  southwestern  Arkansas.  An. 
Rep.  Geol.  Surv.  Arkansas,  1888,  vol.  11,  p.  131  (under  the  name  of 
Ostrea  Franklini ),  pi.  5,  fig.  1-10  (not  pi.  5,  fig.  11-18;  pi.  6,  fig. 
19-27;  pi.  7,  fig.  28-30). 


On  a New  Exogyra  from  Del  Rio  Clay  5 

line  to  immature  specimens  of  Ex.  texana , with  5 to  8 radial 
folds  on  the  anterior  slope,  a distinct  umbonal  ridge,  and  a 
steep  anterior  slope.  The  upper  valve  is  practically  smooth. 
This  form  seems  to  be  intimately  related  to  Exogyra  Bous- 
singaulti  d’  Orb.1  which  occurs  approximately  in  the  cor- 
responding horizon  of  Europe.  A similar  form  has  been 
found  in  the  Aptian  of  San  Juan  Raya,  Puebla,  Mexico. 

This  species  seems  to  have  branched  off  into  several  forms 
in  the  next  higher  division  of  the  Trinity  formation,  some 
of  which  have  been  described  and  very  imperfectly  figured 
by  Cragin  as  Ex.  pauper  cula2 3  and  Ex.  weather  for  densis.^ 

These  species  are  quite  frequent  in  the  Alternating  beds 
(Glenrose),  the  middle  and  upper  part  of  the  Trinity  form- 
ation. Both  seem  to  be  related  to  Ex.  Hilli  and  Ex.  Bous- 
singaulti,  although  the  distinguishing  feature  in  Ex.  pau- 
percula  is  that  the  beak  becomes  free  from  the  rest  of  the 
shell  as  in  Ex.  arietina.  Ex.  paupercula  has  only  2 to  4 
irregularly-topped,  angular,  radial  folds  on  the  lower  valve, 
while  the  upper  valve  seems  to  be  smooth.  I have  not  been 
able  to  see  the  original  specimens. 

Much  more  similar  to  the  Ex.  Boussingaulti  group  is  the 
Ex.  weather fordensis  (pi.  1,  fig.  1,  2)  with  a strong  um- 
bonal ridge,  6 to  12  oblique  plications  on  the  anterior  slope, 
and  a greater  number  of  narrow,  subradiate,  or  curved  pli- 
cations on  the  posterior  slope.  The  upper  valve  is  smooth, 
but  the  margin  is  often  scalloped  corresponding  to  the  end- 
ing of  the  ribs  on  the  lower  valve. 

This  is,  at  least,  what  I take  to  be  Ex.  weather  fordensis, 
a species  which  has  not  been  very  well  figured.  In  the 
collection  of  the  University  of  Texas  exists  a number  of 
specimens  collected  by  Taff  at  one  quarter  of  a mile  west  of 
Weatherford,  labeled  E.  Boussingaulti  d’Orb.  This  species 
certainly  is  very  similar  to  the  French  form  and  a near  rela- 
tive of  it,  and  at  the  same  time  also  of  Ex.  Hilli.  It  does 


iA.d’  Orbigny,  Voy.  dans  l’Amerique  merid.  t.  Ill,  4me  part,  Pal., 
p.  91,  pi.  18,  fig.  20;  pi.  20,  fig.  8,  9. 

Idem,  Paleont.  frang.,  Terr.  Cret.  t.  Ill,  p.  702,  pi.  468. 

2Cragin,  loc.  cit.,  p.  186,  pi.  30,  fig.  7,  8. 

3Idem,  ibidem,  p.  188,  pi.  45,  fig.  7-10. 


6 


University  of  Texas  Bulletin 


not  seem  possible  to  prove  that  it  is  the  type  of  Ex.  weather- 
fordensis  but  it  appears  at  least  to  be  very  similar  to  the 
specimens  described  and  figured  by  Cragin ; and  it  certainly 
proves  that  a very  near  relative  of  Ex.  Boussingaulti  lived 
in  the  Texas  sea  at  about  the  epoch  of  the  European  species. 
The  specimens  from  a place  four  miles  west  of  Montell, 
also  cited  by  Cragin,  may  belong  to  the  same  species,  but 
they  are  mainly  upper  valves,  and  not  very  characteristic. 

These  last  two  species  seem  to  grow  larger  than  Ex.  Hilli 
and  to  a certain  degree  lead  over  to  Ex.  texana  and  Ex. 
arietina.  The  first  of  these  two  species  is  found  well  de- 
veloped in  the  Walnut  clays,  the  base  of  the  Fredericksburg 
formation.  This  species  has  been  described  and  figured  by 
several  authors,  first  by  Roemer,1  then  by  Conrad,  Gabb, 
Coquand,  White,  Hill  and  Vaughan,  and  by  myself.2  The 
species  is  nearly  related  to  Ex.  flabellata  Goldfuss  of  the 
Cenomanian  of  Europe,  but  it  is  in  general  broader,  the  ribs 
are  more  numerous,  and  the  ridge  is  nearer  to  the  anterior 
side ; the  European  species  is  generally  a little  younger  than 
Ex.  texana , although  this  latter  passes  through  quite  a num- 
ber of  horizons.  In  the  Walnut  clay  it  is  associated  with 
Engonoceras,  Schloenbachia  group  of  Sch.  Belknapi,  and 
Schloenbachia  group  of  Sch.  acutocarinata,  and  these  beds 
probably  represent  the  Vraconnian  or  the  Albian.  It  is 
found  also  in  the  Comanche  Peak  limestone  and  the  Ed- 
wards limestone;  both  still  belonging  to  the  Vraconnian  or 
Albian.  At  the  Cerro  Muleros  it  occurs  throughout  the 
whole  Vraconnian. 

It  should  not  be  overlooked  that  the  Comanche  Peak  lime- 
stone seemingly  contains  another  species  of  Exogyra,  di- 
rectly derived  from  the  main  tribe  and  exceedingly  similar 
to  Ex.  Boussingaulti;  it  is  distinguished  from  Ex.  texana  by 
its  smooth  upper  valve,  is  not  very  frequent,  and  I have  not 
seen  more  than  a very  few  specimens. 

Ex.  texana  is  certainly  derived  from  the  tribe  of  Ex. 
Boussingaulti  represented  by  Ex.  weatherfordensis , but  the 
younger  species  grows  much  broader,  the  umbonal  ridge 

1Roemer,  Kreidebild.  v.  Texas,  1852,  p.  69,  pi.  10,  fig.  la-le. 

2Bbse,  Cerro  de  Muleros,  Bol.  Inst.  geol.  de  Mexico,  25.  P.  112, 
pi.  20,  fig.  14-16;  pi.  21,  fig.  1-11;  pi.  22,  fig.  1-9. 


On  a New  Exogyra  from  Del  Rio  Clay  7 

moves  nearer  to  the  anterior  margin,  which  becomes  ex- 
ceedingly steep,  while  the  posterior  slope  becomes  flattened 
or  even  concave.  The  upper  valve  develops  a great  number 
of  somewhat  irregular  radial  ribs,  the  umbonal  ridge  be- 
comes very  pronounced  and  the  anterior  slope  quite  steep. 
A conscientious  study  of  the  forms  from  different  horizons 
may  show  that  even  within  the  species  a certain  develop- 
ment takes  place,  in  so  far  as  the  umbonal  ridge  is  nearer 
to  the  anterior  margin  in  the  older  specimens  than  in  the 
younger  ones,  and  that  the  ribs  grow  coarser  in  the  indi- 
viduals found  in  the  higher  horizons. 

Ex.  texana  nearly  always  occurs  in  great  numbers  and 
with  it  begins  the  rich  development  and  subdivision  of  the 
principal  tribe. 

Before  we  go  any  farther  we  shall  have  to  mention  an- 
other form  developed  during  thq  Albian  or  the  Vraconnian 
and  apparently  the  ancestor  of  several  younger  species. 
This  is  the  form  described  by  Cragin1  as  Ex.  plexa.  Under 
this  name  Cragin  seems  to  have  united  at  least  two  differ- 
ent species;  I refer  his  name  to  one  of  these  which  looks 
entirely  like  an  enlarged  juvenile  specimen  of  Ex.  arietina 
(compare  the  description  of  this  species  given  below).  The 
exact  types  could  not  be  found,  but  there  is  sufficient  ma- 
terial from  the  original  localities.  (Compare  pi.  1,  figs.  3, 
4.)  I regard  as  the  type  the  specimen  figured  by  Cragin 
in  his  figures  3,  5,  6 (not  4).  It  is  entirely  covered  with 
fine  radial  ribs  which  cross  the  prominent  umbonal  ridge 
obliquely  as  in  the  juvenile  specimens  of  Ex.  arietina.  The 
specimens  occur  in  the  bed  of  Ex.  texana  below  the  Kiami- 
tia  clays  on  the  Texas  and  Pacific  railroad,  three  miles  west 
of  Benbrook.  The  whole  shell  is  spirally  curved  similar  to 
the  young  Ex.  arietina  although  the  size  is  much  larger. 
The  beak  is  still  pressed  down  against  the  body  of  the  shell, 
but  a further  spiral  development  would  detach  the  beak 
from  the  rest  of  the  valve. 

This  species  has  probably  developed  from  the  group  of 
Ex.  Boussingaulti  (Ex.  weatherfordensis)  losing  the  thick 

1Cragin,  loc.  cit.,  p.  187,  pi.  30,  fig.  3-6. 


8 


University  of  Texas  Bulletin 


folds  and  developing  fine  ribs,  but  retaining  the  high  um- 
bonal  ridge. 

In  the  same  strata  we  find  another  species,  of  which  a 
specimen  not  very  characteristic  has  been  illustrated  by 
Cragin  in  his  fig.  4.  The  upper  part  (about  15  mm.  in 
height)  is  practically  of  the  same  form  and  ornamentation 
as  Ex.  plexa  typ.  but  from  there  on  it  begins  to  develop 
on  the  anterior  side  four  to  five  strong  radial  folds  begin- 
ning near  the  umbonal  ridge  and  going  down  obliquely  with 
the  ridge  to  the  antero-inferior  margin.  They  are  much 
stronger  and  sharper  than  shown  in  Cragin’s  figure  and  are 
covered  by  fine  radial  ribs.  They  are  fainter  on  the  mould 
and  there  appear  smooth.  As  our  material  is  not  sufficient 
to  allow  a complete  description  we  shall  designate  the  species 
as  Ex.  nov.  sp.  aff.  plexa.  (PI.  1,  fig.  5). 

Ex.  plexa  seems  to  lose  the  fine  ribs  on  the  lower  margin 
in  larger  specimens,  as  is  shown  by  an  individual  from  the 
original  locality.  This  feature  is  still  more  evident  in  larger 
specimens  found  at  the  base  of  the  Fort  Worth  limestone  in 
Duck  Creek,  Grayson  County.  This  is  evidently  a younger 
form  of  the  same  group,  but  possibly  a different  species  or 
variety.  It  grows  much  larger  than  the  type,  shows  ap- 
proximately the  same  ornamentation  on  the  umbonal  region, 
but  becomes  entirely  smooth  on  the  inferior  margin. 

Another  form  from  the  Kiamitia  clays  found  on  little 
Mineral  Creek,  north  of  Pottsboro,  Grayson  County,  shows 
an  ornamentation  very  similar  to  that  of  Ex.  plexa  on  the 
umbonal  region,  but  develops  a rather  deep  furrow  along 
the  umbonal  ridge  on  the  posterior  side  and  several  obtuse 
folds  covered  with  fine  radial  ribs  on  the  anterior  side  near 
the  antero-inferior  margin.  It  is  most  probably  a descend- 
ant of  Ex.  nov.  sp.  aff.  plexa,  mentioned  above  (PI.  1,  fig.  6.) 

About  the  development  of  Exogyra  in  the  Georgetown 
formation,  i.  e.,  the  lower  and  middle  part  of  the  Cenoman- 
ian, little  is  known. 

There  is  a large  species  frequently  found  in  this  forma- 
tion and  it  has  generally  been  called  Ex.  americana  or  Ex. 
Walkeri.  It  was  originally  described  by  Marcou  as  Gry- 
phaea  sinuata  var.  americana,  and  Cragin  cites  it  as  Ex. 


On  a New  Exogyra  from  Del  Rio  Clay  9 

americana  Marcou.  Unfortunately,  only  very  large  speci- 
mens are  described  and  figured,  but  the  individual  illus- 
trated by  Marcou  shows  that  the  younger  specimens  must 
have  strong,  fold-like,  radial  ribs  in  the  umbonal  region. 
Therefore  I presume  that  this  broad  and  flat  species  with 
its  obtuse  ridge  near  the  anterior  margin  developed  from  a 
broad,  coarsely-ribbed  group,  probably  one  derived  from 
Ex.  texana . 

Exogyra  becomes  exceedingly  frequent  on  top  of  the 
Georgetown  formation  in  the  Del  Rio  clay  which  represents 
part  of  the  upper  Cenomanian. 

The  principal  species  is  Ex.  arietina  Roem.  which  we  have 
redescribed  farther  on.  It  is  evidently  a descendent  of  Ex. 
plexa;  it  retains  the  ornamentation  of  this  species  and  its 
form  on  the  umbonal  region  and  in  the  very  young  indi- 
viduals, but  later  on  becomes  entirely  smooth  and  its  beak 
becomes  detached  because  the  whole  valve  coils  spirally. 

A second  species  is  Ex.  Cartledgei  nov.  sp.,  described  be- 
low. It  certainly  was  derived  from  Ex.  nov.  sp.  aff.  plexa , 
developing  the  strong  radial  ribs  still  more,  while  the  beak 
became  somewhat  detached  from  the  rest  of  the  shell  by  the 
coiling  of  the  valve.  The  strong  umbonal  ridge  is  still  in 
existence,  but  the  fine  ribs  on  the  beak  were  lost ; or  at  least 
are  not  preserved  on  the  specimens  I have  in  hand.  This 
species  grows  much  larger  than  either  Ex.  nov.  sp.  aff. 
plexa  or  Ex.  arietina. 

Cragin1  described  another  species  from  the  Del  Rio  clay 
which  he  called  Ex.  Drakei.  Unfortunately  his  figures  are 
very  deficient,  but  his  originals  show  that  the  species  is 
entirely  different  from  Ex.  Cartledgei.  It  is  covered  with 
irregular  but  strong  ribs  on  the  lower  valve,  not  really 
coiled,  but  rather  bent  over  to  one  side,  as  shown  in  Cragin’s 
figure  11.  The  upper  valve  is  very  similar  to  that  of  Ex. 
arietina  and  Ex.  Cartledgei. 

In  the  next  higher  horizon,  the  Buda  limestone  and  the 
corresponding  strata  of  the  Cerro  de  Muleros,  which,  ac- 
cording to  the  echinoid  fauna  described  by  Whitney,  and 


iCragin,  loc.  cit.,  p.  184,  pi.  29,  fig.  8-11. 


10 


University  of  Texas  Bulletin 


the  ammonites,  represents  the  very  uppermost  part  of  the 
Cenomanian,  several  Exogyras  occur  which  are  larger  than 
most  of  those  in  beds  below,  with  only  the  possible  excep- 
tion of  Ex.  americana. 

The  species  found  in  the  Buda  limestone  is  Ex.  Clarki 
Shatt.,1  but  the  specimens  figured  by  Shattuck  represent 
only  medium-sized  individuals  and  the  species  should  be  re- 
described and  figured.  It  is  a very  broad  and  not  very 
thick  species  very  similar  to  Ex.  americana;  the  medium- 
sized specimens  show  rather  strong  radial  ribs,  while  the 
mature  specimens  are  almost  smooth.  Very  juvenile  speci- 
mens do  not  seem  to  have  been  found.  The  species  evi- 
dently is  a direct  descendent  of  the  older  Ex.  americana. 

In  the  corresponding  strata  of  the  Cerro  de  Muleros  an 
Exogyra  is  found  in  great  numbers,  which  I took  formerly 
to  be  identical  with  Ex.  Clarki  and  which  on  account  of  its 
great  similarity  with  Ex.  ponderosa  I described  as  Ex.  pon- 
derosa  var.  Clarki.2  The  medium-sized  specimens  of  this 
species  really  are  extremely  similar  to  Ex.  Clarki  while  the 
full  grown  individuals  are  entirely  different.  I therefore 
rename  the  species  from  the  Cerro  de  Muleros  and  call  it 
Exogyra  Whitneyi  in  honor  of  Prof.  F.  L.  Whitney,  whose 
beautiful  studies  about  the  echinoid  and  mollusk  fauna  of 
the  Buda  limestone  have  given  us  the  first  idea  of  its  rich 
fauna  and  its  real  age. 

I have  figured  especially  the  juvenile  and  medium-sized 
specimens  of  Ex.  Whitneyi  in  the  work  cited  above.  If  we 
compare  figs.  5,  6,  7,  11  on  plate  26  with  specimens  of 
Ex.  plexa,  we  can  find  nearly  no  difference.  Comparing 
figs.  4,  8,  10,  12  on  the  same  plate  with  Ex.  Cartledgei  and 
Ex.  Drakei  we  see  at  once  that  the  similarity  is  extremely 
great,  although  the  beak  is  not  quite  as  much  coiled  spirally 
as  in  Ex.  Cartledgei.  The  upper  valve  figured  in  fig.  9 of 
the  same  plate  is  very  similar  to  that  of  Ex.  Cartledgei. 
The  mature  forms  are  entirely  different  from  the  younger 

1Shattuck,  Buda  Limestone,  Bull.  U.  S.  Geol.  Surv.  no.  205.  1903. 
p.  22,  pi.  10,  11. 

2E.  Bose,  Cerro  d£  Muleros,  p.  115,  pi.  23,  fig.  17;  pi.  24,  fig.  6; 
pi.  25,  fig.  8;  pi.  26,  fig.  4-11. 


On  a New  Exogyro,  from  Del  Rio  Clay  11 

ones ; the  ribs  mostly  are  destroyed  by  erosion  and  the  shell 
becomes  entirely  smooth,  the  beak  detached  from  the  body. 
It  brings  to  mind  at  once  the  elongate  varieties  of  Ex.  yon- 
derosa  but  notwithstanding  the  great  similarity  between  the 
two  species  I have  become  convinced  that  they  should  be 
separated  specifically  on  account  of  the  somewhat  different 
form  of  the  younger  specimens,  the  generally  broader  shape 
of  the  mature  Ex.  yonderosa,  and  the  extremely  different 
age  of  the  beds  in  which  both  species  occur. 

Those  small  individuals  from  Cerro  de  Muleros  which  I 
have  taken  to  be  juvenile  forms  of  Ex.  Whitneyi  show  an 
astounding  similarity  to  a small  Exogyra  extremely  fre- 
quent in  the  Mainstreet  limestone  of  Denison.  This  form 
has  been  frequently  cited  under  the  name  of  Exogyra  arie- 
tina,  but  is  easily  distinguished  from  it  by  its  rather  strong 
ribs  and  the  form  of  the  beak  pressed  against  the  body  of 
the  shell.  The  real  Ex.  arietina  occurs  in  a somewhat  higher 
horizon  of  the  same  locality ; that  is  to  say,  in  the  Grayson 
Marls.  The  similarity  between  the  small  Exogyra  of  the 
Mainstreet  limestone  and  the  small  individuals  from  the  red 
sandstone  of  Cerro  Muleros  is  so  great  that  I have  become 
somewhat  doubtful  if  these  latter  forms  are  really  the  ju- 
venile forms  of  Ex.  Whitneyi  and  not  perhaps  a different 
species  identical  with  or  very  similar  to  the  small  Exogyra 
in  the  Mainstreet  limestone,  although  they  certainly  occur 
together  with  Ex.  Whitneyi  in  the  red  sandstone  of  Cerro 
Muleros.  It  is  of  course  possible  that  the  small  Exogyra 
of  the  Mainstreet  limestone  is  at  the  same  time  a prede- 
cessor of  Ex.  Whitneyi  and  of  Ex.  arietina. 

A species  very  nearly  related  to  Ex.  Whitneyi  is  Ex. 
ferox,  if  it  is  not  only  a variety.  Ex.  ferox  was  described 
by  Cragin1 ; unfortunately  his  figures  are  so  deficient  that 
one  cannot  get  an  adequate  idea  of  the  shape,  and  the  upper 
valve  of  the  original  has  been  lost.  The  lower  valve  is  very 
similar  to  that  of  the  mature  Ex.  Whitneyi,  but  is  still  more 
elongate;  no  closer  comparison  can  be  made  before  the  ju- 

1Cragin,  loc.  cit.,  p.  185,  pi.  32,  fig.  1;  pi.  33,  fig.  5;  pi.  34,  fig.  1; 
pi.  36,  fig.  6. 


12 


University  of  Texas  Bulletin 


venile  stages  of  Ex.  ferox  have  been  found  and  described. 
The  species  was  found  in  the  so-called  lower  Cross  Timber 
(Woodbine)  sands,  which  correspond  in  age  probably  to  the 
Buda  limestone;  at  least,  they  also  belong  in  their  lower 
part  to  the  upper  Cenomanian. 

It  is  difficult  to  say  to  what  group  belongs  the  form  cited 
by  Cragin1  as  Ex.  columbella  Meek.  It  certainly  has  noth- 
ing to  do  with  the  type  of  that  species.  The  specimen  which 
came  from  the  lower  Cross  Timber  sands  of  Timber  Creek, 
two  miles  below  the  Dallas-Lewisville  Road,  Denton  County, 
is  so  much  corroded  that  the  surface  appears  nearly  smooth, 
but  on  close  inspection  one  can  easily  see  that  it  had  been 
covered  by  thick,  rounded,  rather  strong  ribs.  It  might  be 
a very  young  individual  belonging  to  the  group  of  Ex. 
Clarki. 

From  the  next  higher  beds,  the  Eagle  Ford  shales,  which 
correspond  to  the  Turonian,  very  few  fossils  have  been  de- 
scribed in  Texas,  and  among  these  only  one  Exogyra  is 
cited  under  the  name  of  Ex.  columbella  Meek.  This  is  a 
rather  small  form  with  thin  shell  and  covered  by  small, 
quite  regular,  radial  ribs,  which  bifurcate  at  the  umbonal 
ridge.  It  seems  to  be  very  possible  that  this  species  is  a 
branch  of  the  Ex.  Clarki  group,  if  it  is  not  directly  derived 
from  Ex.  arietina  through  the  so-called  Ex.  columbella 
Cragin.  This  may  only  be  decided  when  larger  collections 
in  the  Eagle  Ford  shales  or  the  upper  part  of  the  Wood- 
bine sands  shall  have  been  made.  In  Colorado  a large 
species,  Ex.  suborbiculata  Lam.,  occurs,  which  as  Stanton 
justly  remarks,  is  intimately  related  to  the  European  group 
of  Ex.  columba,  but  this  larger  form  has  not  yet  been  found 
in  Texas. 

Also  in  the  next  higher  formation,  the  Austin  Chalk,  very 
few  Exogyras  are  known,  although  they  can  be  found  in 
great  numbers  in  it.  The  Austin  Chalk  corresponds  in  its 
lower  part  to  the  Emscherian,  in  its  middle  to  the  lower 
Santonian,  and  in  its  upper  part  to  the  middle  Santonian. 
I have  not  seen  any  Exogyra  in  the  lower  part,  but  it  is 


Cragin,  loc.  cit.,  p.  184. 


On  a New  Exogyra  from  Del  Rio  Clay  13 

possible  that  Ex.  laeviuscula  Roemer  or  a related  form  oc- 
curs there,  as  it  certainly  does  in  the  middle  portion.  This 
very  characteristic  form  is  entirely  smooth,  but  if  the 
younger  specimen  figured  by  Roemer  in  PI.  9,  fig.  3c,  really 
belongs  to  this  species,  we  might  suppose  that  it  is  derived 
from  Ex.  nov.  sp.  aff.  plexa  through  Ex.  Cartledgei  and 
Ex.  columbella  Cragin  (not  Meek)  having  lost  entirely  the 
finer  ribs. 

An  undescribed  and  unstudied  small  Exogyra  is  very  fre- 
quent in  the  middle  part  of  the  Austin  Chalk  (zone  of 
Mortoniceras  texanum)  on  the  Rio  Grande. 

In  the  upper  part  of  the  Austin  Chalk  near  Austin  we 
find  a great  number  of  a large  Exogyra  which  commonly 
has  been  called  Ex.  ponderosa,  although  it  is  specifically 
quite  different.  It  has  a broad  and  not  very  convex  lower 
valve,  with  a rounded  ridge  and  an  extremely  steep  slope 
on  the  anterior  margin,  and  is  very  similar  to  the  large 
specimens  of  Ex.  Clarki  and  to  a certain  degree  to  Ex.  amer- 
icana.  These  species  with  very  low  right  valves  probably 
form  an  independent  branch  and  are  derived  from  Ex.  tex- 
ana.  I have  not  seen  any  of  this  tribe  in  higher  strata  of 
Texas,  but  a near  relative,  Ex.  tamulica  Stol.,  appears  in 
the  higher  Senonian  of  India. 

The  Exogyras  of  the  higher  strata  of  Texas,  the  Taylor 
marls  (upper  Santonian),  Navarro  beds  (Campanian)  and 
the  higher  Escondido  beds  (Maestrichtian)  are  very  little 
known,  practically  only  two  species  having  been  described : 
Ex.  ponderosa  Roem.  from  the  Taylor  marls  and  Ex.  costata 
Say  from  the  Navarro  beds,  which  seems  to  continue  into 
the  base  of  the  higher  Escondido  beds. 

Exogyra  ponderosa  has  been  first  and  very  well  described 
and  figured  by  Roemer.1  In  recent  years  it  has  been  re- 
described and  figured  by  Stephenson.-  His  figures  are 
very  characteristic  but  unfortunately  he  has  not  tried  to 
describe  and  figure  the  development  of  the  species  from  the 

Roemer,  Kreidebild.  v.  Texas,  p.  71,  pi.  9,  fig.  2. 

2L.  W.  Stephenson,  Cret.  dep.  on  the  Eastern  Gulf  region.  U.  S. 
Geol.  Surv.  Prof.  Paper  81,  1914,  p.  46,  pi.  13,  fig.  5-7;  pi.  14;  pi.  15, 
fig.  1-3. 


14 


University  of  Texas  Bulletin 


youngest  to  the  mature  individuals.  Roemer  mentions  that 
specimens  about  2.5  cm.  long  show  distinct,  unequal,  radial 
folds  which  begin  to  grow  indistinct  near  the  margin  of  the 
valve.  Stephenson's  PL  13,  fig.  5 shows  clearly  this  kind 
of  ribs  on  the  beak  of  a medium-sized  specimen.  If  we 
imagine  this  beak  detached  from  the  valve  and  in  the  form 
of  a young  specimen,  it  would  have  exactly  the  shape  and 
ornamentation  of  a young  specimen  of  our  young  Ex.  Whit- 
neyi  from  the  Cerro  de  Muleros,  and  be  extremely  similar 
to  the  young  of  Ex.  arietina  and  to  the  mature  specimens 
of  Ex.  plexa.  Stephenson  (loc.  cit.  p.  49,  pi.  15,  fig.  4;  pi. 
16,  fig.  1,  2)  has  described  a number  of  shells  as  Ex.  pon- 
derosa  var.  erraticostata  Steph.  It  will  be  rather  difficult 
to  sustain  this  variety  because  the  figure  of  Roemer's  type 
shows  very  similar  ribs  and  thus  should  be  part  of  this 
variety. 

Ex.  costata  has  been  quite  frequently  described  and  fig- 
ured ; recently  Stephenson1  has  very  fully  described  the  ma- 
ture specimens  and  also  has  illustrated  these  profusely. 
Unfortunately  also  in  this  case  we  lack  the  exact  knowledge 
of  the  ornamentation  of  very  young  specimens.  The  species 
is  possibly  derived  from  Ex.  ponderosa  or  at  least  from  a 
form  of  which  Ex.  ponderosa  is  a branch,  but  this  cannot 
be  proven  at  the  present  time.  Specimens  should  be  espe- 
cially studied  in  the  zone  where  Ex.  ponderosa  and  Ex.  cos- 
tata appear  to  occur  together  and  where  the  real  antecessor 
of  the  latter  species  may  be  found. 

The  preceding  sketch  of  the  evolution  of  Exogyra  in  the 
Texas  Cretaceous  necessarily  has  to  be  deficient,  incomplete 
and  in  a great  part  hypothetical,  but  at  least  it  shows  that 
all  the  species,  even  the  largest  which  are  practically 
smooth,  came  originally  from  a rather  small  costate  form; 
and  that  the  great  diversity  of  forms  in  the  upper  strata  is 
simply  due  to  the  subdivision  of  a tribe  represented  at  the 
base  by  forms  that  are  intimately  related  to  each  other  and 
at  the  same  time  to  Ex.  Boussingaulti  of  the  European 
Aptian.  It  shows  also  that  some  of  the  large  species  in  the 

Stephenson,  loc.  cit.  n.  50  p1.  16.  fig.  3,  4;  pi.  17,  fig.  1,  2;  pi.  18; 
pi.  19,  fig.  1-4;  pi.  20  fig.  1. 


On  a New  Exogyra  from  Del  Rio  Clay  15 

higher  horizons  may  not  be  intimately  related,  notwith- 
standing the  very  similar  shape,  but  rather  be  convergent 
forms. 

A monograph  of  the  Texas  Cretaceous  Exogyras  would 
probably  show  a still  much  greater  variety  of  forms  which 
were  derived  from  the  same  original  tribe,  and  at  the  same 
time  it  would  not  at  all  be  difficult  to  demonstrate  that  in 
Europe,  Northern  Africa  and  Asia  quite  a similar  evolution 
has  taken  place. 


16  University  of  Texas  Bulletin 


Probable  relationships  of  the  species  of  Exogyra  in  Texas. 


On  a New  Exogyra  from  Del  Rio  Clay 


17 


DESCRIPTION  OF  SPECIES 
Exogyra  Cartledgei  nov.  sp. 

Pl.  I,  fig.  7-13;  PL  II,  fig.  1-4;  Pl.  III,  fig.  1-8. 

Shell  medium-sized,  very  thick,  elongate  to  sub-oval,  some- 
what oblique  up  to  the  beak,  which  is  spirally  coiled  down- 
ward and  outward. 

Inferior  valve. 

Shape  very  variable,  elongate  to  obliquely  suboval  up  to 
the  beak,  strongly  convex,  the  highest  part  forming  an 
obtuse,  curved,  umbonal  ridge  which  follows  approximately 
the  middle  line  of  the  height  of  the  shell,  and  which  disap- 
pears toward  the  inferior  margin  of  the  valve.  The  slope 
toward  the  anterior  margin  is  sometimes  much  steeper  than 
toward  the  posterior  side. 

Beak  generally  spirally  twisted  or  coiled  downward  and 
outward;  sometimes  pressed  against  the  body  of  the  shell, 
sometimes  almost  entirely  free  in  the  shape  of  a ramshorn. 
The  beginning  of  the  beak  is  never  free,  but  always  pressed 
against  the  shell,  which  shows  that  in  the  juvenile  stage 
the  beak  was  not  detached  from  the  rest  of  the  valve  and 
that  the  development  in  the  form  of  a ramshorn  is  the 
latest  stage  caused  by  the  spiral  coiling  of  the  valve  during 
the  later  stages.  The  point  of  the  beak  often  shows  a scar, 
due  to  its  having  been  attached  to  some  small  object,  such  as 
shells,  etc. 

The  ornamentation  consists  of  about  fifteen  coarse  long- 
itudinal ribs  which  on  each  of  the  slopes  (anterior  and 
posterior)  are  nearly  parallel  on  the  upper  half  of  the  valve. 
The  series  on  the  anterior  side  is  not  parallel  to  that  on  the 
posterior  one,  but  forms  an  angle  of  about  40  degrees.  On 
the  umbonal  ridge  the  two  series  are  united  by  an  inter- 
vening space  covered  by  intercalated,  bifurcating  ribs.  The 
ribs  on  the  anterior  side  form  a wide  angle  with  the  axis 
of  the  umbonal  ridge  but  on  the  last  part  of  the  beak  they 


18 


University  of  Texas  Bulletin 


become  nearly  parallel  to  the  ridge.  The  opposite  side  of 
the  beak  always  appears  to  be  entirely  smooth,  which  prob- 
ably is  in  part  due  to  the  state  of  preservation.  The  ribs 
are  crossed  by  lines  of  growth  and  by  strong  lamellae  which 
give  them  a scaly  aspect.  The  lines  of  growth  and  lamellae 
cover  also  the  beak. 

The  ligamental  groove  is  generally  spirally  curved,  deep, 
broad,  triangular,  very  long  to  very  short,  according  to  the 
shape  of  the  beak,  limited  on  both  sides  by  a ridge.  Below 
the  groove  on  the  posterior  side  is  a shelf-like  fold  finely 
crenulated,  on  the  anterior  side  a similar  one  but  rounded 
and  less  distinct.  The  shell  outside  of  these  ridges  is  also 
finely  crenulated  along  the  upper  part  of  the  animal  cavity, 
the  crenulation  becoming  very  faint  on  the  lower  half  until 
it  disappears,  entirely.  The  muscular  impression  is  deep 
and  very  near  the  posterior  margin.  The  cavity  often  ex- 
tends somewhat  into  the  beak. 

Upper  valve. 

Rather  thick,  slightly  convex  to  flat,  operculiform,  sub- 
ovate  with  a nearly  flat  spiral  twist,  the  beak  being  near 
the  margin.  Beak  very  little  prominent,  nearly  pressed 
down  to  the  rest  of  the  shell.  Sometimes  there  is  a very 
obtuse,  spirally  curved  umbonal  ridge  which  disappears  to- 
ward the  postero-inferior  margin.  On  the  posterior  side 
right  near  the  beak  is  a distinct  depression. 

On  a well  preserved  specimen  the  ornamentation  consists 
of  numerous  concentric  growth  lines  and  lamellae  which 
cover  the  whole  surface.  The  lamellae  are  not  of  circular 
form,  but  show  an  angular  prolongation  on  the  umbonal 
ridge.  Where  this  is  absent  the  lamellae  follow  a more  or 
less  elliptical  course.  Fine  radiating  ribs  are  visible  on  the 
postero-superior  part  of  the  shell  in  the  region  close  to  the 
beak.  The  margins  are  distinctly  crenulated. 

The  ligamental  groove  is  mostly  broad  and  flat,  seldom 
narrow  and  deep ; in  the  first  case  strongly  spirally  curved, 
in  the  second  case  much  less  so.  In  the  first  case,  the  lig- 
amental groove  is  almost  parallel  to  the  superior  margin; 
in  the  second  case  it  nearly  forms  a right  angle  with  it. 


On  a New  Exogyra  from  Del  Rio  Clay  19 

This  seemingly  depends  on  the  thickness  of  the  valve.  To- 
ward the  interior  and  posterior  side  of  the  groove,  a striated 
protuberance  elevates  itself  more  or  less  highly ; it  is  oppo- 
site the  depression  formed  by  the  striated  shelf  and  cren- 
ulated  margin  of  the  lower  valve,  and  probably  fits  into  it. 

The  muscular  impression  is  deep  and  near  the  posterior 
side,  far  below  the  region  of  the  beak. 

Relation  to  other  species: 

Ex.  Cartledgei  has  a certain  similarity  to  Ex.  arietina, 
but  its  strong  ribs  and  large  size  make  it  easy  to  distinguish 
the  two.  It  probably  has  been  derived  from  the  same  tribe, 
that  of  Ex.  plexa , or  a similar  form,  as  has  been  explained 
in  the  first  chapter  of  this  paper. 

Occurrence: 

The  species  has  been  found  very  frequently  in  the  Del 
Rio  clay  in  a horizon  about  10  to  30  feet  below  the  Buda 
limestone.  The  Del  Rio  clay  has  at  this  place  a thickness 
of  120  feet  or  more.  It  is  associated  with  Nodosaria  tex- 
ana,  which  occurs  in  abundance  above  it,  Gryphaea  sp.,  En- 
allaster  cf.  bravoensis,  and  Hemiaster  sp.  According  to 
Dr.  Udden,  Exogyra  arietina  is  rare  at  this  locality  but 
was  noted  at  a level  not  far  from  the  middle  height  of  the 
Del  Rio  clay. 

Locality: 

Reed  Plateau,  point  almost  exactly  one  mile  south  from  the 
Chisos  Mining  Company’s  mine,  in  Brewster  County,  Texas. 

Exogyra  arietina  Roemer 
PL  IV,  fig.  1-18;  PI.  V,  fig.  1-23. 

1852.  Ferd.  Roemer,  D'e  Kreidebildungen  von  Texas  und  Hire  or- 
ganischen  Einschliisse.  Bonn.  P.  68,  PI.  8,  fig.  10. 

Roemer’s  description  of  this  species  is  very  careful  and 
his  illustrations  are  quite  good,  but  figures  of  the  juvenile 
stages  of  the  species  are  lacking,  as  these  were  not  given 
overmuch  importance  by  the  paleontologists  of  that  time. 


20 


University  of  Texas  Bulletin 


Roemer  remarks  that  the  surface  of  the  lower  valve  in 
the  region  of  the  beak  is  covered  by  delicate  longitudinal 
striae  interrupted  by  the  lamellae  of  growth  and  which  gen- 
erally can  be  seen  only  in  the  more  juvenile  specimens,  the 
region  of  the  beak  being  more  or  less  corroded  in  the  larger 
individuals. 

A study  of  well  preserved  specimens  of  Ex.  arietina  of 
different  ages  shows  at  once  that  Roemer  is  absolutely  cor- 
rect in  his  description,  but  also  that  the  development  of  the 
species  shows  three  clearly  marked  stages. 

Leaving  aside  the  protoconch  which  is  of  the  size  of  about 
a common  pinhead,  the  first  stage  of  development  (PI.  V, 
fig.  7-10)  has  the  following  character:  In  shells  up  to 

about  3 mm.  in  length,  the  surface  does  not  show  a trace  of 
ribs,  even  where  not  the  slightest  corrosion  has  taken  place ; 
it  is  only  covered  by  rounded,  concentric,  relatively  broad 
and  not  very  distinct  folds  and  the  growth  lines.  At  this 
size,  the  posterior  side  of  the  shell  is  distinctly  flat  with  the 
beak  pressed  against  the  rest  of  the  valve;  only  the  very 
first  part  of  the  beak  in  a length  of  0.5  to  1.0  mm.  elevates 
itself  a little  above  the  surface  of  the  shell.  The  umbonal 
ridge  is  relatively  sharp  and  high  and  reaches  from  the 
beak  to  the  postero-inferior  margin.  The  anterior  side 
forms  an  angle  of  about  50  degrees  with  the  posterior  side, 
and  is  rounded  in  height  as  well  as  in  width.  This  angle 
between  the  two  sides  causes  the  prominent  umbonal  ridge. 
The  outline  of  the  valve  is  triangular-suboval  at  this  stage. 

The  second  stage  is  represented  by  specimens  of  a length 
of  about  10  mm.  or  a little  more  (PL  V,  fig.  11-16).  In 
these  individuals  the  shell  of  the  first  part  of  the  beak,  up 
to  about  3 mm.  from  its  point,  is  of  course  smooth,  but  on 
the  next  wrinkles  of  growth,  fine  radial  ribs  appear  sud- 
denly in  the  number  of  about  30  to  35.  They  are  very  dis- 
tinct on  the  anterior  side,  the  umbonal  ridge,  and  the  greater 
part  of  the  posterior  side,  but  become  indistinct  in  this  lat- 
ter region  on  the  surface  near  the  end  of  the  beak.  The 
ribs  reach  higher  on  the  anterior  than  on  the  posterior  side, 
and  pass  obliquely  over  the  umbonal  ridge.  The  lamellae 


On  a New  Exogyra  from  Del  Rio  Clay  21 

of  growth  begin  to  develop,  interrupting  the  ribs  and  im- 
parting to  them  the  aspect  of  roof  tiles. 

The  umbonal  ridge  is  as  prominent  as  in  the  preceding 
stage  at  least  in  the  umbonal  region,  but  toward  the  post- 
ero-inferior  region  it  becomes  rounded  and  less  distinct. 

The  shape  of  the  shell  begins  to  change.  It  has  no  longer 
the  triangular  form  but  begins  to  coil  spirally.  In  connec- 
tion with  this  circumstance  the  growth  lines  and  lamellae 
no  longer  form  a perfect  elliptical  curve,  but  begin  to  show 
in  their  course  a distinct  protuberance  or  tongue-like  pro- 
longation on  the  umbonal  ridge. 

The  next  stage  represents  the  beginning  of  the  mature 
development  (PI.  IV,  fig.  10-15;  PL  V,  fig.  1-3).  The  ribs 
disappear  about  as  suddenly  as  they  began,  the  shell  becomes 
smooth  and  is  only  covered  by  lines  of  growth  and  lamellae 
which  appear  more  distinct  the  more  the  shell  grows.  They 
no  longer  form  a simple  curve,  but  are  rather  wavy,  especial- 
ly on  the  posterior  side  and  a little  less  on  the  anterior  side, 
showing  a pronounced  tongue-like  prolongation  or  protu- 
berance in  their  outline  on  the  umbonal  ridge.  The  wavy 
appearance  of  the  lamellae  on  both  sides  corresponds  to  the 
development  of  shallow  furrows  (PL  V,  fig.  4,  17),  one  more 
distinct  on  the  anterior  side  and  one  generally  less  so  on 
the  posterior  side. 

The  shape  of  the  shell  now  changes  very  rapidly,  coiling 
spirally  so  that  the  umbonal  region  becomes  twisted  and  de- 
tached from  the  rest  of  the  valve. 

Exceptionally  it  can  be  observed  that  very  faint  and  some- 
what irregular  longitudinal  ribs  appear  again  on  larger 
shells  up  to  a distance  of  about  35  mm.  from  the  beak, 
measured  along  the  umbonal  ridge  (PL  V,  fig.  17)*. 

In  the  last  stage  of  mature  specimens  the  shell  attains  its 
characteristic  shape  similar  to  a ramshorn,  as  described  by 
Roemer  (PL  IV,  fig.  1-9,  16-18;  PL  V,  4-6,  17). 

The  opercular  upper  shell  does  not  change  essentially 
(PL  IV,  fig.  4;  PL  V,  fig.  16,  18-23).  It  appears  to  have 
the  same  character  from  the  size  of  about  2 mm.  to  the 
largest  mature  forms  with  a length  of  25  mm.  and  more.  The 
valve  is  sometimes  nearly  flat,  always  with  a rather  deep 


22 


University  of  Texas  Bulletin 


depression  on  the  posterior  side  near  the  spirally  coiled 
beak,  the  point  of  which  is  pressed  down  against  the  sur- 
face of  the  shell.  Sometimes  this  valve  is  entirely  oval, 
especially  in  immature  individuals ; in  other  specimens  it  is 
distinctly  spirally  coiled,  developing  a relatively  high  um- 
bonal  ridge. 

The  ornamentation  of  the  surface  consists  only  of  spiral 
lines  of  growth  and  lamellae.  Only  the  superior  margin 
of  the  umbonal  region  is  finely  crenulated.  Traces  of  fine 
crenulation  show  sometimes  on  the  inferior  margin. 

The  interior  of  the  lower  valve  does  not  change  mater* 
ially  from  the  immature  stage  to  the  well  developed  spec- 
imen. The  ligamental  groove  is  always  very  narrow  and 
deep,  spirally  coiled,  and  follows  the  superior  margin.  A 
faintly  crenulated  ridge  is  below  it,  the  margin  on  the  upper 
half  of  the  cavity  being  always  slightly  crenulated. 

The  cavity  continues  into  the  beak,  more  or  less. 

The  muscular  impression  is  near  the  posterior  side  and 
close  to  the  region  of  the  beak. 

The  interior  of  the  upper  valve  does  not  change  materially 
from  the  immature  stages  to  the  final  development  of  the 
species.  The  ligamental  groove  is  very  long,  very  narrow 
and  deep,  spirally  coiled,  follows  the  superior  margin  of  the 
valve,  and  obliquely  crosses  the  spiral  lamellae  of  growth. 
The  space  between  the  groove  and  the  superior  margin  is 
finely  crenulated. 

The  muscular  impression  is  strong  and  exactly  under  the 
umbo,  as  has  already  been  observed  by  Roemer. 

Occurrence : 

Del  Rio  clay. 

Locality  of  the  specimens  studied: 

Shoal  Creek,  Austin,  Texas. 


EXPLANATIONS  OF  PLATES 


Plate  I 

Fig.  1,  2... Exogyra  weatherfordensis  Cragin. — Glenrose 
formation.  One-fourth  of  a mile  west  of 
Weatherford,  Parker  County,  Texas.  Page  5 

Fig.  3,  4 . . . Exogyra  plexa  Cragin. — From  bed  with  Exo- 
gyra texana  below  the  Kiamitia  clays. 
Texas  and  Pacific  Railway,  three  miles  west 
of  Benbrook,  Tarrant  County,  Texas.  Page  8 

Fig.  5 Exogyra  nov.  sp.  aff.  plexa  Crag.  From  bed 

with  Exogyra  texana  below  the  Kiamitia 
clays.  Texas  and  Pacific  Railway,  three 
miles  west  of  Benbrook,  Tarrant  County 
Page  8 

Fig.  6 Exogyra  sp.  aff.  plexa  Crag. — Kiamitia  c by. 

Little  Mineral  Creek,  north  of  Pottsboro, 
Grayson  County,  Texas. 

Fig.  7-13 ..  .Exogyra  Cartledgei  nov.  sp. — Del  Rio  clay. 

Reed  Plateau,  about  one  mile  from  the 
Chisos  Mining  Company’s  mine  in  Brewster 
County,  Texas Page  17 

Fig.  7-9,  11-13,  beaks  of  the  lower  shell  showing  the  dif- 
ferent stages  of  development.  Fig.  10,  Lig- 
amental  groove  of  a large  and  slender  speci- 


men. 


Plate  I 


Plate  II 


Fig.  1-4 . . . Exogyra  Cartledgei  nov.  sp. — Del  Rio  clay. 

Reed  Plateau,  about  one  mile  south  from  the 
Chisos  Mining  Company's  mine,  in  Brewster 

County,  Texas  Page  17 

Fig.  1 . . large  slender  shell,  lower  valve.  • 

Fig.  2 . . inside  of  same. 

Fig.  3 . . broad  adult  shell  with  coiled  beak. 

Fig.  4.  .inside  of  same. 


Plate  II 


Plate  III 


Fig.  1-8 . . Exogyra  Cartledgei  nov.  sp. — Del  Rio  clay.  Reed 
Plateau  about  one  mile  from  the  Chisos  Min- 
ing Company's  mine,  in  Brewster  County, 
Texas Page  17 

Fig.  1 . . upper  valve. 

Fig.  2 . . inside  of  the  same. 

Fig.  3,  6,  7 . . surface  of  upper  valves. 

Fig.  4,  8.  .inside  of  upper  valves. 

Fig.  5 . . inside  of  lower  valve  showing  a strongly 
curved  beak  and  a corresponding  ligamental 
groove. 


Plate  III 


Plate  IV 


Fig.  1-18.  . .Exogyra  arietina  Roemer. — Del  Rio  clay. 

Shoal  Creek,  at  Austin,  Texas Page  17 

Fig.  1-3 . . adult  normal  specimen  shown  in 
three  positions. 

Fig.  4-6 . . adult  normal  specimen  shown  in 
three  positions. 

Fig.  7-9.. adult  normal  specimen  shown  in 
three  positions. 

Fig.  10-12 . . young  normal  specimen  shown  in 
three  positions. 

Fig.  16-18.  .adolescent  stage  shown  in  three 
positions. 


Plate  IV 


< 


I 


. 


' 


Plate  V 


Fig.  1-23 . . . Exogyra  arietina  Roemer. — Del  Rio  clay. 
Shoal  Creek  at  Austin,  Texas. 


Fig. 

1-3. 

.young  normal  specimen  shown  in 
three  positions. 

Fig. 

4.  .. 

.young  individual  showing  a strong 
spiral  groove. 

Fig. 

5..  . 

.aberrant  adult  specimen  with  ex- 
ceptionally coiled  beak. 

Fig. 

6..  . 

.aberrant  adult  specimen  with 
strongly  coiled  beak. 

Fig. 

7.. . 

.very  young  specimen,  natural  size. 

Fig. 

8... 

. the  same,  strongly  amplified,  show- 
ing a smooth  surface  on  the 
greater  part  of  the  shell,  ribs 
beginning  to  appear  at  the  mar- 

gin. 

Fig.  9. . . . very  young  specimen,  natural  size. 

Fig.  10..  . .the  same,  strongly  amplified,  show- 
ing the  smooth  surface  of  the 
shell  at  this  stage  of  develop- 
ment. 

Fig.  11..  . .very  young  specimen,  natural  size. 

Fig.  12, 13 . the  same,  strongly  amplified  to 
show  the  ornamentation.  The 
shell  is  smooth  on  the  point  of 
the  beak,  and  develops  radial 
ribs  farther  down. 

Fig.  14 ...  . very  young  specimen,  natural  size. 

Fig.  15, 16. the  same,  strongly  amplified  to 
show  the  ornamentation.  The 
shell  is  smooth  on  the  point  of 
the  beak,  and  develops  radical 
ribs  farther  down. 

Fig.  17. . . . adult  specimen  twice  amplified  to 
show  the  ornamentation  on  the 
point  of  the  beak,  and  its  simi- 
larity with  that  of  the  small  in- 
dividuals illustrated  in  fig.  11- 
16. 

Fig.  18-23. upper  valves  of  small  specimens. 

The  slit  apparently  limiting  the 
umbo  in  figure  19  is  due  to  frac- 
turing and  is  not  natural. 


Plate  V 


n it  u i 

■ !ff;m!!;ii'  fit 

B96-819-6m 

University  of  Texas  Bulletin 

No.  1931:  June  1,  1919 


THE  GEOLOGY  OF  TARRANT  COUNTY 

By 

W.  M.  WINTON  AND  W.  S.  ADKINS 


BUREAU  OP  ECONOMIC  GEOLOGY  AND  TECHNOLOGY 
J.  A.  Udden,  Director 

DIVISION  OP  ECONOMIC  GEOLOGY 

J.  A.  Udden,  Head  of  the  Division 


Published  by  the  University  Six  Times  a Month,  and  Entered  as 
Second-Class  Matter  at  the  Postoffice  at  Austin,  Texas, 

Under  the  Act  of  August  24,  1912. 


GEOLOGY 


The  benefits  of  education  and  of 
useful  knowledge,  generally  diffused 
through  a community,  are  essential 
to  the  preservation  of  a free  govern- 
ment. 

Sam  Houston 


Cultivated  mind  is  the  guardian 
genius  of  democracy  ....  It  is  the 
only  dictator  that  freemen  acknowl- 
edge and  the  only  security  that  free- 
men desire. 


Mirabeau  B.  Lamar 


Page 

LIST  OF  ILLUSTRATIONS . 5 

GENERAL  DESCRIPTION  OF  THE  AREA 7 

PHYSIOGRAPHY  AND  TOPOGRAPHY 9 

Topographic  Divisions  of  Tarrant  County 9 

Black  Prairie 9 

Ea'stern  Cross  Timbers 10 

Grand  Prairie 11 

Western  Cross  Timbers 12 

Drainage.  . * 12 

Geological  Map 14 

Type  Localities  in  Tarrant  County 15 

FOSSILS  AS  HORIZON  MARKERS : 16 

Mode  of  Preservation 16 

Possibility  of  Recurrent  Horizons 18 

Utility  of  Fossils  in  Interpreting  Well  Logs 19 

Table  of  Identification  Values  of  Comanchean  and  Cretaceous 

Fossils 21 

THE  GEOLOGICAL  SECTION 24 

Description  of  Formations 25 

Pennsylvanian . 25 

Comanchean 25 

Trinity  Division 25 

Trinity  (Basement)  Sands 26 

Glenrose  Limestone 26 

Paluxy  Sands 26 

Fredericksburg  Division 26 

Washita  Division 33 

Kiamitia  Marl . . 33 

Duck  Creek  Formation 39 

Fort  Worth  Formation 51 

Denton  Marl 58 

Weno  Formation 61 

Pawpaw  Formation 67 

Mainstreet  Formation # 69 

Grayson  Marl 72 

Woodbine  Formation 74 

Upper  Cretaceous 82 

Eagleford  Shales 82 

Cenozoic  and  Recent 84 


ECONOMIC  GEOLOGY. 
Resources  of  Location 


84 

85 


4 


University  of  Texas  Bulletin 


Page 


Resources  of  Soil 87 

Resources  of  Plant  and  Animal  Life 88 

Resources  of  Crude  Material 89 

Limestone  Industries 89 

Gravel  and  Sand 91 

Clay  Industries 92 

Possibilities  of  Oil  and  Gas 95 

Water  Resources 97 


DIP,  ALTITUDES,  WELL  LOGS,  ETC 100 

Dip, 100 

Altitudes  in  Tarrant  County 101 

Precise  Levels  in  Tarrant  County 102 

Description  of  New  Magnetic  Station 107 

Log  of  Well  at  Polytechnic,  Texas 107 

Log  of  well  near  Mansfield,  Texas 115 


INDEX 119 

TOPOGRAPHIC  MAP  OP  THE  T.  C.  U.  VICINITY 122 

GEOLOGICAL  MAP  OF  TARRANT  COUNTY 122 


LIST  OF  ILLUSTRATIONS 


FIGURES 

Pag© 


Fig.  1.  Columnar  Section  of  the  Frederickbui  g Limestone  in 
the  Valley  of  the  West  Fork  of  the  Trinity  River  near  the 
Lake  Worth  Dam 31 

Fig.  2.  Columnar  Section  of  the  Kiamitia  Formation  in  Cut  on 

the  Azle  Road,  eight  miles*  northwest  of  Fort  Worth 36 

Fig.  3.  Columnar  Section  of  the  Duck  Creek  Formation  in  Cuts 

near  Forest  Park,  Fort  Worth 41 


Fig.  4.  Columnar  Sections  of  the  Fort  Worth  Limestone. 
A.  On  Sycamore  Creek,  northwest  corner  of  Glenwood 
Park.  B.  Eastward  facing  Exposure  in  a run  one-half 
mile  east  of  Texas  Christian  University  and  one-half  mile 


south  of  Forest  Park,  Fort  Worth .53 

Fig.  5.  Columnar  Section  of  the  Denton,  Weno  and  Pawpaw 
formations  on  Sycamore  Creek,  3 miles  southwest  of  Fort 
Worth 63 

Fig.  6.  Columnar  Section  of  Portions  of  the  Woodbine  Forma- 
tion in  Cuts  of  the  Rock  Island  Railway  between  Tarrant 
Station  and  the  Tarrant-Dallas  County  Line 79 


PLATES 

(Inside  back  cover) 

Plate  1.  Goodland  Limestone  (top  of  Fredericksburg  Division) 
at  the  Lake  Worth  Dam,  8 miles  northwest  of  Fort  Worth. 

Plate  2.  Fig.  1.  Top  of  Goodland  (Fredericksburg)  Lime- 
stone, looking  east  from  near  Benbrook. 

Figure  2.  Goodland  Limestone,  Stove  Foundry  Road,  4 
miles  west  of  Fort  Worth. 

Plate  3.  Fig.  1.  Top  of  the  Goodland  Limestone,  looking  east 
from  near  Benbrook. 

Fig.  2.  Terraces  in  the  Fredericksburg  Division. 

Fig.  3.  Terraces  in  the  Basal  Washita  Division. 

Plate  4.  Fig.  1.  Base  of  the  Fort  Worth  Limestone,  which  un- 
derlies the  business  section  of  the  city  of  Fort  Worth. 
Fig.  2.  Gate  posts  and  flower  beds  in  Forest  Park,  ibuilt  of 


6 


University  of  Texas  Bulletin 


the  large  Ammonite,  Desmoceras  brazoense,  of  the  Duck 
Creek  Limestone. 

Plate  5.  Pig.  1.  The  large  Ammonite,  Schloenbachia  species  J., 
which  characterizes  the  Fort  Worth  Limestone. 

Pig.  2.  Illustration  of  the  terms  “cast”  (left)  and  “mold” 
(right) . 

Plate  6.  Fort  Worth  Limestone  in  Excavation  at  the  northwest 
corner  of  Eighth  and  Houston  streets. 


THE  GEOLOGY  OF  TARRANT  COUNTY 

BY  W.  M.  WTNTON  AND  W.  S.  ADKINS1 
GENERAL  DESCRIPTION  OF  THE  AREA 

Tarrant  County  is  in  the  third  tier  of  counties  of  the  east 
central  province  of  Texas,  and  is  included  within  the  belt  of 
densest  population  in  the  state.  The  estimated  population  of 
the  county,  January,  1919,  is  about  148,000,  of  which  130,000  is 
concentrated  in  the  city  of  Fort  Worth.  This  city,  like  the  cities 
of  Dallas,  Waco,  Austin,  and  San  Antonio,  lies  on  the  outcrop 
of  the  calcareous  formations  of  the  Cretaceous  system.  Lime- 
stone areas  have  always  been  the  areas  of  the  greatest  industrial 
development  and  its  accompaniment  of  concentrated  popula- 
tion; and  of  limestone  areas  those  of  the  Cretaceous  have  in  the 
past  been  the  most  favorable.  Many  writers  have  commented 
on  the  curious  relationship  between  centers  of  civilization  and 
the  outcrops  of  Cretaceous  rocks.  In  fact,  even  today,  a map  of 
the  world  showing  the  areas  of  greatest  human  development 
would  bear  a striking  resemblance  to  the  map  of  the  world ’s  out- 
crops of  Cretaceous  rocks.  Many  explanations  have  been  at- 
tempted of  this  suggested  connection.  The  simple  facts  seem 
ample.  Cretaceous  limestones  furnish  an  abundant  water  supply, 
a firm  substratum,  break  down  into  rich  soil,  furnish  material 
for  the  construction  of  roads  and  buildings,  and  by  their  mode 
of  weathering  furnish  a land  surface  which  is  a perfect  com- 
promise between  the  level  surface  most  favorable  to  the  develop- 
ment of  elaborate  transportation,  and  the  rolling  surface  most 
favorable  for  perfect  drainage. 

Tarrant  County  epitomizes  in  a way  the  agricultural  indus- 
tries of  the  state.  The  western  part  of  the  county  is  in  the 
rolling  short-grass  prairie  region  of  West  Texas,  which  is  typical 
grazing  land;  while  the  eastern  part  of  the  county  is  made  up 
of  timbered  country  and  bottom  lands,  including  a typical  cotton- 
farming country.  In  a biological  sense  the  county  lies  at  the 
junction  of  the  humid  and  semi-arid  divisions  of  the  Lower 
Austral  life  zone.  Its  location  implies  a great  mixture  of  wild 
life,  both  plant  and  animal;  and  such  a condition  exists.  Be- 


1 The  order  of  names  does  not  in  any  way  indicate  seniority. 
Ms.  accepted  June  1,  1919,  published  March  1920. 


8 


Umversity  of  Texas  Bulletin 


sides  this,  the  county  lies  at  what  might  be  considered  the  junc- 
tion of  life  zones  in  a north-south  distribution;  that  is,  it  con- 
tains life  forms  which  belong  both  to  the  sub-tropical  area  and 
to  the  warmer  temperate  zones.  There  is  probably  no  other 
region  in  the  state  which  shows  such  a variety  of  wild  life, 
especially  of  plant  life,  exhibiting  a blending  of  semi-arid  with 
humid  forms  and  temperate  with  sub-tropical  forms. 

Tarrant  County  lies  roughly  between  longitude  W.  97°  1.8' 
and  longitude  W.  97°  32.6',  and  latitude  N.  32°  33.3'  and  lati- 
tude N.  32°  59.3',  giving  it  an  area  of  about  903  square  miles. 
The  magnetic  declination  at  the  station  of  the  United  States  Coast 
-and  Geodetic  Survey  on  the  Texas  Christian  University  campus 
at  Fort  Worth  is  9°  27.4'  east.  On  the  ordinary  pocket  compass 
used  by  hunters,  boy  scouts,  and  field  geologists,  reading  to  a 
minimum  of  two  degrees,  the  declination  is  ten  degrees  to  the 
east.  That  is,  when  the  pocket  compass  is  held  so  that  the 
needle  points  to  10°  east,  the  zero  or  north  mark  of  the  compass 
is  pointing  to  the  true  north. 

The  entire  county  is  covered  by  rocks  belonging  to  a single 
geological  age — the  Cretaceous,  about  equally  divided  between 
lower  Cretaceous,  or  more  properly  Comanchean,  and  Upper 
Cretaceous.  The  underlying  rocks  dip  gently  toward  the  south- 
east. The  rocks  are  hard  chalky  limestones,  soft  limestones, 
marls,  and  red  sandstones.  The  dip  of  the  strata  gives,  in  gen- 
eral, long  gentle  slopes  on  the  southeast  side  of  the  uplands, 
where  the  surface  of  the  ground  approximates  the  dip  of  the 
underlying  rocks,  and  it  gives  rather  abrupt  slopes  on  the  north- 
west side  of  such  uplands,  Avhere  the  successive  ledges  of  the 
different  formations  emerge  from  below  the  surface.  This  is 
the  so-called  “cuesta”  type  of  topography.  Despite  its  recogniz- 
able nature,  with  the  gentle  dip  plains  on  one  side  and  steep 
bluffs  on  the  other  side,  the  fact  must  be  kept  in  mind  that  in 
many  cases  the  “dip  plains”  are  not  true  dip  plains,  and  the 
abrupt  bluffs  are  not  always  the  “ends”  of  formations.  This 
statement  is  made  here  because  many  writers  in  discussing  this 
feature  of  North  Texas  topography  have  taken  rather  too  liter- 
ally the  proposition  that  this  cuesta  type  of  topography  indi- 
cates exactly  the  position,  thickness,  and  attitude  of  the  forma- 
tions. 


The  Geology  of  Tarrant  County 


9 


PHYSIOGRAPHY  AND  TOPOGRAPHY 


The  underlying  geological  formations,  aside  from  climatic 
factors,  are  the  most  important  natural  features  in  determining 
the  configuration  of  a region,  and  therefore,  also,  its  possibili- 
ties for  cultivation  and  its  suitability  for  a dense  population, 
location  of  large  cities,  and  other  cultural  developments. 

The  area  included  in  Tarrant  County  illustrates  this  intimate 
relation  between  the  geology  of  a country  and  its  surface 
features.  A complexity  of  surface  features  is  possible  with  a 
combination  of  alternate  hard  and  soft  strata,  an  even  dip,  and 
a well  developed  drainage.  These  factors  result  in  a striking 
diversity  of  land  forms  and  a pleasing  variety  of  scenery. 

The  highest  point  in  the  county  is  in  the  western  part,  where 
an  elevation  of  1050  feet  above  sea  level  is  reached.  The  lowest 
point  is  where  the  Trinity  River  passes  out  of  the  county  to  the 
east.  This  latter  point  has  an  elevation  of  450  feet,  giving  the 
entire  county  a maximum  relief  of  600  feet.  In  general  this  is 
represented  by  a gradual  slope  to  the  east,  broken  by  the  west- 
ward facing  escarpments.  The  escarpments  are  steep  and  con- 
spicuous, but  the  much  longer  and  gentler  eastern  slopes  are 
not  so  readily  noticed.  The  trip  from  Fort  Worth  to  Dallas 
by  the  automobile  pike  is  decidedly  downhill  in  its  entirety, 
the  fall  being  about  160  feet  in  a distance  of  a little  more  than 
thirty  miles ; but  because  of  the  several  conspicuous  escarpments 
which  must  be  ascended  in  traveling  east,  the  average  individual 
fancies  that  he  is  traveling  mostly  up  hill. 

TOPOGRAPHIC  DIVISIONS  OP  TARRANT  COUNTY 

The  area  included  within  Tarrant  County  consists  of  four 
broad  belts,  two  prairie  strips  alternating  with  two  sandy  strips 
or  “ cross  timber”  zones.  These  are  as  follows,  from  east  to 
west:  the  Black  Prairie,  the  Eastern  Cross  Timbers,  the 

Grand  Prairie,  and  the  Western  Cross  Timbers. 

The  Black  Prairie  has  only  a small  part  of  the  lower  and 
western  portion  of  its  great  area  in  Tarrant  County.  This  black 
land  prairie  is  underlain  by  the  whole  Cretaceous  series,  above 


10 


University  of  Texas  Bulletin 


the  Woodbine  sand1.  Due  to  the  dip  of  the  strata  toward  the 
Gulf  Coast,  this  is  the  lowest  of  the  belts  in  altitude,  but  the 
highest  in  the  geological  series.  It  is  a gently  rolling  slope  with 
a treeless  surface.  The  soil  is  black,  waxy,  and  carbonaceous. 
It  is  deep  and  of  a superior  grade.  Because  of  the  deep  soil, 
the  cuesta  topography  is  not  prominent,  but  even  in  the  soft 
marly  shales,  as  in  the  eastern  part  of  Tarrant  County,  the 
escarpment  and  dip  plains  are  recognizable.  The  Eagleford 
subdivision  of  the  Black  Prairie  is  separated  from  the  Austin 
chalk  subdivision  by  the  prominent  Austin  chalk  escarpment 
which  extends  for  hundreds  of  miles  across  Texas  parallel  to 
the  general  direction  of  outcrop  of  the  strata,  and  is  finely  ex- 
posed in  White  Cliff  on  the  Fort  Worth-Dallas  pike,  a few  miles 
west  of  Dallas.  This  westward-facing  escarpment  overlooks  the 
successive  strips  of  Eagleford  prairie,  which  arise  from  under 
it,  and  ascending  westward  divide  the  prairie  by  small  crests 
which  are  themselves  miniature  escarpments.  These  correspond 
to  the  subdivisions  of  the  Eagleford  formation.  Approaching 
Fort  Worth  from  the  east,  these  rise  in  altitude  until  just  east 
of  Arlington  the  top  of  the  Woodbine  sand  emerges  from 
underneath  the  basal  member  of  the  Eagleford  shales. 

The  Eastern  Cross  Timbers  are  underlain  by  a homogeneous 
strip  of  red  sandstone  composing  the  Woodbine  formation;  and 
are  heavily  timbered  with  black  jack  oaks  and  post  oaks.  The 
exposure  of  the  Woodbine  formation  is  an  important  catchment 
area  for  water,  as  noted  by  Dr.  Hill,  furnishing  artesian  water  in 
areas  far  to  the  east  of  Tarrant  County  where  this  sand  is  deep  * 
underground.  A conspicuous  feature  of  the  rock  under  the 
Cross  Timbers  is  its  tendency  to  form  large  lens-like  masses  and 
to  show  cross  bedding.  These  features  should  be  considered  very 
cautiously  by  prospective  oil  drillers  and  are  explained  and 
discussed  under  the  section  on  the  Woodbine  formation  At  the 
western  border  of  the  Cross  Timbers  where  the  limestone  emerges, 
an  interesting  feature  is  the  string  of  small  ‘ ‘ islands 9 9 or  outliers 
of  the  red  sandstone.  These  form  the  numerous  “ Brushy  Knobs”, 
seen  in  this  strip  from  the  Red  River  to  the  Brazos.  Some  of 

1 The  formations  referred  to  in  this  discussion  are  subsequently 
more  fully  described  under  the  section  on  Geology. 


The  Geology  of  Tarrant  County 


11 


these  ‘‘knobs”  are  distinctly  peak-like,  and  are  possibly  due  to 
lenticular  masses  in  the  sandstone. 

The  Grand  Prairie  has  a surface  which  is  varied  correspond- 
ing to  the  diverse  groups  of  rock  strata  underlying  it.  The 
columnar  section  (fig.  1-6)  indicates  roughly  a series  of  lime- 
stone layers  alternating  with  marl  members.  The  limestones 
weather  out  as  upland  surfaces  which  are  more  or  less  flat,  ex- 
cept for  the  effects  of  erosion,  while  the  softer  marl  groups  break 
down  more  readily  under  weathering  and  are  exposed  as  slopes 
connecting  the  levels  of  the  limestones  above  and  below.  This  pro- 
duces a terrace  effect  which  is  one  of  the  features  of  the  region. 
The  limestones  do  not  always  or  even  usually  weather  out  into 
dip  plains  whose  surfaces  are  entirely  upon  a single  stratum. 
This  sort  of  plain  is  rare,  despite  frequent  reference  to  such 
occurrences  in  the  geological  literature  of  this' region  The  most 
common  upland  slope  is  an  erosion  slope  dipping  in  the  direc- 
tion of  the  greatest  dip  of  the  underlying  strata  but  also  slanting 
off  towards  the  drainage  and  consequently  not  lying  entirely  on 
one  stratum,  but  including  many  successive  strata.  The  state- 
ment that  the  cuesta  type  of  topography  prevails  must  be  ac- 
cepted with  reserve  so  far  as  Tarrant  County  is  concerned. 

The  Grand  Prairie  has  two  areally  prominent  members,  the 
Mainstreet  limestone  and  the  Fort  Worth  limestone.  These  to- 
gether make  up  80  per  cent  of  the  total  area ; and  the  other  mem- 
bers of  the  series  form  essentially  narrow  strips  connecting  these 
two  with  the  adjoining  areas  and  with  each  other.  For  instance, 
the  Grayson  marl  connects  the  eastern  prairie  strip,  the  Main- 
street  limestone,  with  the  Woodbine  sand.  Although  fifty  feet 
thick,  the  Grayson  is  an  inconspicuous  strip  areally  (exaggerated 
in  mapping)  and  the  formation  is  very  rarely  exposed  or  entirely 
free  from  overwash.  The  Mainstreet  with  the  same  thickness 
forms  a broad  upland  many  miles  wide.  At  many  places  the 
Denison  beds,  the  Denton,  Weno,  and  Pawpaw  formations,  form 
a sharp,  even  slope  connecting  the  Mainstreet  limestone  upland  of 
the  eastern  side  with  the  Fort  Worth  limestone  upland  of  the 
western  side.  Yet  the  thickness  of  the  Denison  beds  far  exceeds 
the  combined  thickness  of  the  Mainstreet  and  Fort  Worth  lime- 
stones. 


12 


University  of  Texas  Bulletin 


The  Western  Cross  Timbers  and  the  adjoining  rocks  to  their 
east  are  complicated  by  the  greatly  dissected  headwaters  of  the 
Trinity  River.  This  dissected  lowland  is  likewise  composite,  and 
is  underlain  by  three  groups  of  strata  in  addition  to  the  river 
alluvium.  The  three  groups  are  timbered  but  are  very  dissimilar 
in  the  rock  composing  them. 

The  upper  and  eastern  strip  is  the  Walnut  formation,  which 
is  conspicuous  by  the  great  amount  of  slabs  composed  entirely  of 
Grypheas,  a-fossil  oyster-like  shell.  The  region  is  considerably 
dissected  into  steep  hills,  deep  laterals  of  the  Trinity  River,  with 
frequent  waterfalls,  cliffs  and  small  rapids.  It  is  well  timbered 
with  post-oak,  black-jack  oak,  and  water  oak.  Next  underlying 
it  geologically,  and  farther  west,  is  a strip  of  Paluxv  sand.  This 
weathers  into  flat  bottom  lands  of  dull  reddish  sand.  The  Glen- 
rose  limestone,  which  is  westward  and  immediately  under  the 
Paluxv  sand,  is  not  exposed  at  the  surface  in  Tarrant  County. 

Throughout  the  four  great  belts  of  country  above  described, 
there  are  two  types  of  gravel,  an  upland  and  a lowland  type, 
and  probably  several  stages  of  alluvium.  These  two  gravels 
are  recognized  commercially  as  “pit”  (upland)  and  “stream” 
(lowland).  In  these  gravels  are  found  the  few  fossils  of  the 
Pleistocene  age  which  are  known  for  this  region,  such  as  mam- 
moths, and  a few  others. 

DRAINAGE 

Tarrant  County  is  drained  entirely  by  the  Trinity  River.  The 
Clear  Pork  of  the  Trinity,  arising  in  Johnson  County  near  the 
Noland’s  River  divide  (Brazos  drainage)  passes  northeast  to 
join  at  Fort  Worth  the  main  branch  of  the  Trinity,  the  West 
Pork,  which  rises  in  Wise  County.  These  two  forks  drain  the 
entire  western  half  of  the  county,  and  the  east  half  is  drained 
by  smaller  laterals  of  the  Trinity,  such  as  Sycamore,  and 
Big  and  Little  Fossil  creeks.  The  Trinity  descends  from  an 
elevation  of  1050  feet  at  the  southwest  corner  of  the  county  to 
450  feet  at  the  Tarrant-Dallas  County  line,  giving  a drop  of 
600  feet  in  40  miles,  or  15  feet  per  mile.  Much  of  this  drop  is 
almost  in  the  strike,  for  where  the  river  runs  directly  across  the 
outcrops  of  the  formations  near  Fort  Worth,  the  rock  strata  are 


The  Geology  of  Tarrant  County 


13 


dipping  eastward  about  ten  times  as  fast  as  the  river.  The  result 
is  that  the  river  in  passing  eastward  crosses  successively 
younger  formations  until  northeast  of  Arlington  it  has  passed 
into  the  Eagleford  shales. 

The  drop  of  the  Trinity  River  is  rather  even  across  Tarrant 
County  where  throughout  its  course  it  has  a timbered  lowland 
alluvial  floodplain,  increasing  in  width  to  five  miles  at  the 
eastern  border.  The  floodplain  is  bordered  by  Goodland  and 
Duck  Creek  escarpments  capped  by  Goodland  and  Fort  Worth 
uplands  west  of  Fort  Worth,  and  east  of  Fort  Worth  by  Weno 
and  Pawpaw  escarpments  capped  by  Mainstreet  uplands.  In 
the  southwest  part  of  the  county  the  Clear  Fork  of  the  Trinity 
passes  through  a Goodland  floodplain  as  described,  but  in  the 
northwest  the  West  Fork  cuts  down  a much  dissected  head- 
waters region.  To  the  east  the  alluvial  floodplain  is  bordered 
by  Cross  Timbered  Woodbine  sands. 

The  strata  of  Tarrant  County  have  suffered  erosion  from  the 
Trinity  drainage  according  to  their  hardness  and  other  char- 
acteristics so  that  the  topography  of  the  areas  bordering  the 
river  valley  shows  three  general  types:  (a)  Dissected  Head- 
waters; (b)  Dissected  Uplands;  (c)  Cross  Timbered  Bottom 
Lands.  These  types  have  distinct  individualities,  divide  the 
county  into  natural  regions  by  producing  each  a different  topog- 
raphy and  scenery,  and  have  differing  possibilities  of  develop- 
ment. 

Dissected  Headwaters  of  the  Trinity : — This  is  an  area  of 
about  one-sixth  that  of  the  county,  on  the  upper  course  of  the 
West  Fork.  The  inequalities  in  hardness  and  composition  of 
the  underlying  Walnut  clays  and  shell  marl  produce  a very 
rough  and  precipitous  headwaters  region  whose  aspect  is  totally 
different  from  that  of  the  uplands.  The  laterals  of  the  Trinity 
run  mostly  in  deeply  cut  narrow  valleys  which  are  tortuous  and 
carry  swift  streams  during  the  rainy  season.  The  hills  make 
indented  and  irregular  ridges  converging  towards  the  river 
valley  and  to  the  east  capped  by  Goodland  limestone.  From 
the  top  of  the  Goodland  escarpment  are  broad  vistas  of  this 
dissected  timbered  landscape  ascending  toward  the  west  and 
uncovering  in  its  turn  the  underlying  sandy  land  of  the  Western 
Cross  Timbers.  (See  page  26.) 


14 


University  of  Texas  Bulletin 


Dissected  Uplands : — These  strips  of  upland  prairie,  mainly 
underlain  by  the  Fort  Worth  and  Mainstreet  limestones  (page 
51)  are  topographic  units  over  the  whole  Cretaceous  area  in 
North  Central  Texas,  where  their  direction  of  outcrop  is  a 
little  east  of  north.  It  is  notable  that  several  railroads  ap- 
proaching Fort  Worth  from  the  north  and  south  have  found  at 
the  same  time  an  even  gradient  and  a firm  substratum  by 
running  in  the  strike  of  these  formations. 

It  has  been  mentioned  that  while  the  outcrops  of  these  up- 
land limestones  and  their  interbedded  marl  formations  conform 
in  general  to  the  cuesta  type  of  topography,  it  is  nearly  always 
with  modification  due  to  erosion  slope  toward  the  drainage  bot- 
toms. The  uplands  are  covered  with  ‘young’  stream  valleys 
cutting  their  way  into  the  original  dip  plains  or  their  remnants 
and  producing  a rolling  topography.  This  upland  dissection  is 
active  and  rapid  in  Tarrant  County,  while  in  the  adjoining 
counties  of  the  Cretaceous  strip  the  exposures  seem  rarer.  As 
the  Trinity  cuts  across  these  limestones  it  produces  the  con- 
spicuous escarpments  which  border  its  valley  for  over  half  its 
course  in  the  county.  The  city  of  Fort  Worth  owes  its  favor- 
able location  to  the  Fort  Worth  limestone  escarpment  as  ex- 
posed along  the  south  bank  of  the  Trinity  and  its  resulting 
good  drainage  and  broad  outlook  over  the  adjacent  valley. 
Although  the  Trinity  is  a small  stream  at  low  water  there  has  been 
considerable  lateral  swing  as  evidenced  by  the  comparatively 
broad  valley,  the  bordering  escarpments,  the  fluviatile  shell  de- 
posits, and  other  features. 

GEOLOGICAL  MAP 

Because  of  the  lack  of  an  areal  map  which  is  reliable  enough 
to  be  used  as  a base  for  geological  mapping,  our  base  map  is 
composite  and  contains  certain  errors  which  affect  the  exact- 
ness of  the  formation  contacts.  In  general  it  may  be  pointed 
out  that  the  formations  most  nearly  follow  the  roads  as  mapped, 
although  even  sight  compass  intersections  show  the  roads  to  be 
slightly  mislocated  in  places.  In  addition  an  even  degree  of 
refinement  has  been  attempted  over  the  whole  area,  and  this 
has  necessitated  a simplification  of  the  geology  at  places  where 
more  detail  could  have  been  shown.  On  the  map  the  finest  pen 


The  Geology  of  Tarrant  County 


15 


line  drawn  represents  a width  of  106  feet,  and  at  many  places 
the  geology  can  be  mapped  more  closely  than  this.  It  is  hoped 
that  there  may  be  produced  an  areal  map  on  which  the  known 
detail  of  Tarrant  County  geology  can  be  represented. 

Tarrant  County  has  been  more  worked  than  any  other  county 
in  the  North  Texas  Comanchean,  except  Grayson  County.  It 
is  the  scene  of  investigations  by  Hill,  Taff,  Leverett,  and  others. 
Part  of  the  county  or  all  of  it  is  included  in  the  following  maps. 

1892  *Taff  and  Leverett:  Cretaceous  Area  North  of  the  Colorado 

River.  3rd  Annual  Report,  Texas  Geological  Survey. 

1898  *Hill:  Black  and  Grand  Prairies  of  Texas.  21st  Annual 

Report,  Part  VII,  U.  S.  G.  S. 

1898  Reconnaissance  Map,  U.  S.  G.  S.,  Fort  Worth  Sheet. 

1912  J.  B.  Hawley,  Topographical  map  of  the  Lake  Worth  region. 

1913  J.  C.  Tra villa:  Road  map  of  Tarrant  County. 

1916  *Geological  Map  of  Texas;  Udden,  Baker  and  Bose.  Bureau 
of  Economic  Geology  and  Technology,  University  of  Texas, 
Bulletin  44.  (Third  edition,  1919). 

Missouri,  Kansas  and  Texas  Railway  of  Texas.  Contour  map 

of  4 square  miles  southeast  of  Fort  Worth,  Texas. 

1918-19  Corps  of  Engineers,  U.  S.  Army.  Progressive  Military  Map, 
Advance  Sheet  487  N,  II  & IV. 

TYPE  LOCALITIES  IN  TARRANT  COUNTY 

Within  this  county  are  found  the  type  localities  of  many  of 
the  species  described  by  Cragin  and  Clark.  For  convenience 
of  reference  there  is  here  given  a list  of  these  localities,  the 
original  terminology  being  quoted: 

Epiaster  elegans  var.  praenuntius  Cragin  1 Comanche  Peak,  Ben- 

brook. 

Epiaster  hemiasterinus  Cragin1 Grayson  marl,  6 miles 

east  of  Fort  Worth. 

Heterodiadema  ornatum  Clark  2 Washita  group,  Fort 

Worth. 

Leptarbacia  argutus  Clark  2 Washita  group,  Fort 

Worth. 


*Geological  map. 

Bragin,  4th  Ann.  Rept.  Tex.  Geol.  Surv.,  1893. 

2 Clark  and  Twitchell,  U.  S.  G.  S.,  Mon.  LIV.,  1915. 


16 


University  of  Texas  Bulletin 


Ophioglypha  texana  Clark  3 Denton  marl,  6 miles 

north  of  Fort  Worth, 
on  the  banks  of  Lit- 
tle Fossil  Creeek. 

Astarte  acuminata  Cragin 1 Weno  marl,  3 y2  miles 

east  of  Fort  Worth. 

Vola  bellula  Cragin1 Half  mile  above  T.  P. 

bridge  on  Sycamore 
Creek,  near  Fort 
Worth. 

Exogyra  plexa  Cragin1 T.  P.  Ry.,  3 miles  east 

of  Benbrook,  20  feet 
below  the  top  of  a 

bed  of  Exogyra  tex- 
ana. 

Stearnsia  robbinsi  White3 Little  Fossil  Creek,  6 

miles  north  of  Fort 
Worth. 

Dalliconcha  invaginata  White  3 Same. 

Cinulia  tarrantensis  Cragin1 Top  of  Exogyra  Texana 

bed,  T.  & P.  Ry.,  2 y2 
miles  east  of  Ben- 

brook, with  Tylosto- 
ma  mutabilis  and 
Cylindrites  formosus. 

Cylindrites  formosus  Cragin1 Same. 

Trichotropis  shumardi  Cragin1 E.  texana  beds,  iy2 

miles  east  of  Ben- 

brook. 

Neritopsis  tramitensis  Cragin1 Woodbine  sands,  top, 

Bear  Creek,  Tarrant 
County,  near  Dallas 
County  line. 

These  localities  are  all  still  recognizable.  The  type  localities 
of  the  Fort  Worth  limestone  (Hill4)  are  practically  obliterated 
by  overwash  and  by  street  grading. 

FOSSILS  AS  HORIZON  MARKERS 

It  is  desirable  to  place  on  record  here  certain  observations 
regarding  the  range  of  the  fossils  found  in  the  formations  ex- 

H^ragin,  4th  Ann.  Rept.  Tex.  Geol.  Surv.,  1893. 

3Hill,  Bull.  Geol.  Soc.  Amer.,  5,  1893,  p.  328. 

* Hill,  Amer.  Jour.  Sci.,  1888;  and  21st  Ann.  Rept.,  U.  S.  G.  S., 
Pt.  VII,  1901,  pp.  259-61. 


The  Geology  of  Tarrant  County 


17 


posed  in  this  county,  and  to  indicate  so  far  as  practicable  the 
relative  utility  of  different  species  as  horizon  markers,  including 
the  mode  of  preservation  of  the  fossils,  and  the  possibility  of 
recurrent  horizons. 

In  Tarrant  County  the  limestones  and  interbedded  marls  fol- 
low each  other  in  alternating  beds,  so  that  the  whole  geological 
column  presents  a remarkable  uniformity.  In  the  first  place, 
the  formations  alternate  between  harder  and  softer  groups  of 
rocks,  so  that  each  limestone  formation  is  overlain  by  a soft 
marly  or  clay  formation.  For  example,  the  Goodland  limestone 
is  overlain  by  the  Kiamitia  marl;  then  comes  the  Duck  Creek 
limestone,  overlain  by  the  Duck  Creek  marl ; then  the  Fort 
Worth  limestone,  overlain  by  the  Denton  shell  marl  ; then  the 
Weno  limestone  and  marl,  overlain  by  the  Pawpaw  clay;  then 
the  Mainstreet  limestone,  overlain  by  the  Grayson  marl.  In  the 
second  place,  within  a formation  are  alternating  lime  and  marl 
strata. 

With  such  a confusing  similarity  of  strata  some  means  of 
locating  the  exact  geological  level  is  necessary  other  than  that 
of  a mere  inspection  of  the  rock.  This  is  furnished  by  certain 
of  the  fossils  contained  in  the  beds.  Of  course  some  fossils 
run  throughout  the  series  or  through  considerable  portions  of  it, 
and  therefore  are  worthless  as  horizon  markers.  Of  these  practi- 
cally nothing  will  be  said  in  this  paper.  Certain  others  are  strictly 
limited  in  their  range  and  occur  only  at  particular  levels.  These 
are  key  fossils,  or  horizon  markers.  If  their  range  of  occurrence 
in  Tarrant  County  is  roughly  less  than  ten  feet  vertically,  the 
range,  in  this  paper,  will  be  called  the  zone  of  occurrence.  If 
it  is  two  vertical  feet  or  less,  it  will  be  referred  to  as  a restricted 
zone.  If  it  is  more  than  ten  feet,  but  of  limited  range,  it  will 
be  referred  to  as  a horizon.  Some  fossils  have  zones  in  which 
they  are  particularly  abundant,  lying  within  horizons  in  which 
they  occur,  but  less  abundantly.  Some  fossils  appear  in  re- 
current zones,  that  is,  zones  between  which  the  fossils  in  ques- 
tion have  never  been  found,  even  after  considerable  search, 
although  admittedly  they  might  occur  there.  It  seems  likely  that 
many  fossils  now  known  only  at  certain  levels  will  be  found 
more  widely  distributed;  and  that  the  main  reliance  is  to  be 
placed  upon  their  zones  of  abundance  as  here  outlined. 


2— Tarrant 


18 


University  of  Texas  Bulletin 


MODE  OF  PRESERVATION 

Fossils  in  this  region  have  been  found  in  the  following  modes 
of  preservation  : 

(a)  In  the  condition  of  lime  compounds,  as  aragonite,  and 

calcite.  This  is  the  most  common  mode.  There  are  two  condi- 
tions: The  original  shell  material  may  be  replaced  by  lime, 

preserving  the  original  appearance  and  the  material  may  be 
either  indurated  or  chalky ; or  the  original  shell  may  be  present, 
sometimes  with  the  nacre  and  lustre  of  the  living  form. 

(b)  In  the  condition  of  iron  compounds,  as  pyrite,  hematite, 
or  limonite. 

(c)  In  the  condition  of  silica,  as  in  some  fossilized  or  opal- 
ized  wood  fragments  and  sandstone  fossils. 

(d)  In  the  condition  of  mud  casts,  consisting  of  compacted 
marl,  often  yellowish,  and  differing  from  ordinary  shells  in 
appearance,  usually  casts  of  the  interior  of  the  original  shell. 
These  casts  are  especially  prevalent  in  the  Goodland  limestone, 
but  are  common  also  in  the  Washita  division.  The  impressions 
may  be  internal,  as  casts;  or  external,  as  moulds. 

If  the  original  shell  is  replaced  by  iron  oxide  it  is  then  called 
an  iron  pseudomorph.  Sometimes,  but  rarely,  calcareous  shells 
are  colored  pinkish. 

POSSIBILITY  OF  RECURRENT  HORIZONS 

Certain  species  which  are  doubtfully  recurrent  will  be  men- 
tioned. The  matter  of  recurrent  forms  is  at  present  debatable, 
and  we  confine  ourselves  to  bare  facts.  To  establish  recurrence 
in  a given  region,  a fossil  must  occur  in  certain  zones  and  not 
between  these,  and  it  must  be  proven  that  the  recurrent  zones 
contain  the  same  species.  If  these  things  are  true,  there  was 
at  intervals  a presumable  migration  of  the  species  in  and  out 
of  the  region  to  one  or  more  “reservoirs”  in  other  regions. 
In  practice  it  is  essential  not  to  confuse  fossils  from  different 
levels  by  supposing  them  to  indicate  the  same  level.  The  chief 
recurrent  forms  are: 

(a)  Kingena  wacoensis  and  other  species.  In  Tarrant  County, 
these  brachiopods  have  been  found  in  only  four  zones:  base  of 
the  Duck  Creek  limestone;  Lower  Kingena  zone  and  upper 
Kingena  zone  of  the  Duck  Creek  marl ; and  base  of  the  Mainstreet 


The  Geology  of  Tarrant  County 


19 


limestone.  Of  these,  the  Kingena  zone  near  the  base  of  the  Main- 
street  limestone  is  the  Kingena  zone  of  the  literature,  and  is 
stated  to  lie  at  the  top  of  the  Georgetown  limestone  at  George- 
town, Austin,  and  other  Central  Texas  localities.  At  Blum,  in 
Hill  County,  near  the  Brazos  River,  brachiopods  occur  near 
the  top  of  the  Gryphea  and  Ostrea  conglomerate  of  the  Denton 
formation,  and  at  the  classic  locality  on  Duck  Creek  north  of 
Denison  and  other  places  on  the  Red  River  they  occur  at  the 
base  of  the  Hamites  zone  in  association  with  fossils  of  this  zone. 
The  Mainstreet  zone  extends  from  the  Red  River  to  the  Rio 
Grande,  according  to  Hill.  The  Duck  Creek  marl  zones  -extend 
for  miles  in  every  direction  from  Fort  Worth,  but  have  not  yet 
been  found  at  the  Red  River.  We  know  of  no  occurrences  be- 
tween the  zones  above  mentioned.  For  practical  purposes,  it 
can  be  said  of  the  Kingenas,  first,  that  they  are  not  confined  to 
one  zone;  and  second,  that  there  are  probably  several  species  of 
brachiopods  in  these  zones. 

(b)  Ostrea  carinata  Lamarck.  The  taxonomy  is  again  con- 
fused here  and  the  Texas  material  requires  critical  study  and 
comparison  with  European  individuals.  This  is  one  of  the  two 
or  three  species  still  remaining  from  a large  number  of  species 
formerly  thought  to  be  common  to  the  Texas  and  European 
Cretaceous.  The  zones  of  recurrence  of  this  species  have  been 
so  greatly  extended  that  they  are  only  doubtfully  recurrent, 
yet  between  these  zones  these  forms  have  not  yet  been  found  in 
the  Texas  region.  In  Europe  where  the  species  ranges  widely 
in  the  Cenomanian  it  is  not  considered  to  be  recurrent. 

(c)  Gervilliopsis  invaginata  (White.)  The  situation  is  es- 
sentially the  same  as  for  Ostrea  carinata. 

(d)  Exogyra  americana  Marcou.  This  large  conspicuous 
oyster  occurs  near  the  top  of  the  Duck  Creek  limestone  near 
Denison  (Dr.  Boese)  and  persistently  in  the  top  of  the  Fort 
Worth  limestone  in  Tarrant  County  and  other  places.  It  has 
so  far  not  been  found  elsewhere. 

UTILITY  OF  FOSSILS  IN  INTERPRETING  WELL  RECORDS 

All  of  the  following  fossils  are  of  much  practical  importance, 
since  even  from  minute  fragments  such  as  are  found  in  well  drill- 


20 


University  of  Texas  Bulletin 


ing,  the  level  may  be  determined  always  approximately,  and 
sometimes  with  exactness.  These  levels  have  been  carefully 
checked  and  their  sequence  verified  in  the  field  in  numerous  local- 
ities and  over  wide  areas.  Where  there  is  variation  within  Tar- 
rant County,  this  is  stated  under  the  discussion  of  the  fossil 
horizon. 

These  key  fossils  will  be  seen  to  unequal  advantage  in  well 
washings.  If,  as  sometimes  estimated,  the  largest  compact 
fragment  likely  to  be  found  in  a standard  rotary  drill  cutting  is 
about  5/8  of  an  inch,  it  is  evident  that  some  fossils  will  survive 
the  drilling  process  intact,  while  others  will  be  ground  to  un- 
recognizable fragments.  Fossils  will  survive  because  of  their 
small  size,  as  some  of  the  small  pvrite  fossils  mentioned  in  this 
paper;  or  because  of  their  hardness,  as  certain  Grypheas;  or 
because  of  both,  as  Kingena;  or  because  of  their  abundance,  as 
some  of  the  Grypheas  in  the  shell  marls;  or  for  other  reasons. 
With  the  number  of  key  fossils  cited  in  this  paper,  it  is  believed 
that  a sufficient  sample  of  one  or  a combination  of  several  fossils 
can  be  had  from  practically  any  level  of  the  Washita  division, 
to  determine  the  level. 

To  assist  in  the  certainty  of  these  determinations,  the  value 
of  the  fossils  for  locating  specific  levels  has  been  designated 
in  the  following  table  of  identification  values.  The  list 

as  given  in  this  table  is  incomplete  and  subject  to  re- 

vision. As  in  the  European  section  the  ammonites  and  echinoids 
are  most  reliable  for  determination  of  stratigraphic  level  and 
other  fossils  are  variable  in  value.  Certain  associations  and 
zones  of  abundance  are  valuable,  as  has  been  explained,  if  recur- 
rences of  the  same  fossil  are  carefully  distinguished  from  each 

other.  (See  page  18).  In  the  following  list,  the  fossils  are 

arranged  within  each  formation,  in  the  order  of  their  occurrence, 
from  top  to  bottom.1 

1 In  this  table  fossils  which  are  most  likely  to  be  found  and 
which  have  not  been  found  at  other  levels  than  those  indicated  are 
marked  with  two  asterisks.  (**) 

Fossils  which  are  less  likely  to  be  found,  but  which  identify 
the  level  indicated  within  narrow  limits,  are  marked  with  one 
asterisk.  (*) 

Fossils  occurring  in  zones  of  abundance  or  other  fossils  occurring 
in  zones  important  for  locating  stratigraphic  levels,  are  left  with- 
out asterisk. 


The  Geology  of  Tarrant  County 


21 


TABLE  OF  IDENTIFICATION  VALUES  OF  COMANCHEAN  AND  CRETA- 
CEOUS FOSSILS1 

Eagleford : 

**Ostrea  belliplicata,  gastropods,  fish  teeth  and  bones. 
Schloenbachia  sp.  P. 

*Acanthoceras  swallovi  (Shumard). 

Woodbine : 

* Conglomerate  of  Ostrea  soleniscus,  Ostrea  carica,  Barbatia  micron- 

ema(?),  Exoygra  sp.,  Aguilera  cumminsi,  Cerithium,  fish  ver- 
tebrae, and  teeth. 

Dexter  sands:  no  fossils  observed. 

Grayson  Marl: 

*Exogyra  sp.  1. 

*Gryphea  mucronata  Gabb. 

*Exogyra  sp.  2 and  Exogyra  arietina  Roemer. 

Pecten  subalpina  (abundant),  Cyphosoma,  Hemiaster  calvini,  etc. 

Mainstreet  Limestone: 

Leiocidaris  (highest). 

**Turrilites  brazoensis  Shumard. 

**Kingena  wacoensis  Roemer  ( ? ) . 

Schloenbachia  sp.  O.,  aff.  inflata. 

*Exogyra  arietina  Roemer. 

Ostrea  quadriplicata  Shumard  (highest). 

*Holectypus  sp.,  aff.  limitis  Boese. 

Ostrea  carinata  Lamarck. 

Pachymya  austinensis  Shumard 

* Pecten  cleburnensis  Adkins  and  Winton  (sp.  1). 

Pecten  sp.  2. 

Pawpaw  Clay: 

Hemiaster  sp.  1;  Nautilus  sp.  1. 

**Pyrite  fauna:  Baculites  sp.;  Scaphites  hilli  Adkins  and  Winton 

(sp.  A);  Hamites  tenawa  Adkins  and  Winton;  Enallaster  sp.  1; 
Salenia  sp.  1;  Trochosmilia  sp.  1;  Turrilites  worthensis  Adkins 
and  Winton  (sp.  A)  and  spp.;  Mortoniceras  sp.  A;  Acanthoceras 
sp.  A. 

* Starfish  zone:  Metopaster  hortensae  Adkins  and  Winton;  Comp- 

tonia  sp.;*  other  starfishes. 

Nodosaria  texana  Conrad. 

Fish  teeth,  vertebrae,  plates. 

Enallaster  sp.  3;  aff.  bravoensis  Boese. 

Weno  Limestono  and  Marl: 

“Quarry  group”:  Ostrea  quadriplicata,  Ostrea  carinata  (abun- 

dant). Gryphea  washitaensis  (abundant),  Homomya  sp. 


1 These  and  other  key  fossils  are  described  and  figured  in:  Adkins 

and  Winton,  Univ.  of  Texas  Bull.  1945. 


22 


University  of  Texas  Bulletin 


♦Pentagonaster  texensis  Adkins  and  Winton  (sp.  1). 

Schloenbachia  spp.  L-M. 

♦Engonoceras  sp.  1 
*Nodosaria  texana  Conrad. 

Venericardia  sp.  1,  Corbula  spp.  1-2,  Turritella  sp.  1. 
♦Cervilliopsis  invaginata  (White). 

♦Pecten  georgetownensis  Kniker  (?),  Turritella  sp.  2,  Remondia 
(?)  acuminata  Cragin,  Hamites  sp.  B,  Cottaldia  sp.  1. 

Denton  Marl: 

♦♦Gryphea  washitaensis  (abundant). 

Ostrea  carinata  (abundant). 

Protocardia  sp.,  Trigonia  sp. 

Fort  Worth  Limestone: 

*Enallaster  longisulcus  Adkins  and  Winton  (sp.  2). 

♦Nerinea  sp.  1. 

♦Exogyra  americana  Marcou. 

Ostrea  carinata  Lamarck. 

*Hemiaster  elegans  Shumard  (abundant). 

♦♦Pecten  bellula  Cragin,, 

♦Schloenbachia  sp.  K (size  of  austinensis  Lasswitz). 

♦♦Holaster  simplex  Shumard  (abundant). 

♦Pecten  sp.  3. 

Schloenbachia  sp.  I. 

Duck  Creek  Marl  and  Limy  Marl: 

* Upper  Kingena  zone. 

Upper  Gastropod  zone:  Cerithium,  Turritella,  Pleurotomaria^ 

Gyrodes  ( ? ) . 

Schloenbachia  sp.  I. 

♦Pecten  wrightii  Shumard. 

♦♦Lower  (Main)  Kingena  zone. 

*Goniophorus  sp.  I. 

* Crania  rp.  1. 

** Hamites  tanima  Adkins  and  Winton;  Hamites  spp.  D-G. 

♦Pinna  sp.  1. 

♦Scaphites  worthensis  Adkins  and  Winton  (sp.  B). 

Lower  Gastropod  Horizon:  Cerithium,  Lunatia,  Cinulia.  Turbo. 

Nerinea  sp.  aff.  pellucida  Cragin,  Schloenbachia  sp. 

Duck  Creek  Marly  Lime  and  Limestone: 

♦Schloenbachia  sn.  I-T.  aff.  trinodosa  Boese. 

* Schloenbachia  sp.  G. 

♦Schloenbachia  sp.  F. 

♦Desmoceras  sp.  B (“brazoensis”,  “graysonense”?). 

♦Desmoceras  sp.  A. 

♦In'oceramus  comancheanus,  I.  munsoni. 

♦♦Hamites  comanchensis  Adkins  and  Winton  (sp.  A);  H.  nokoni& 


The  Geology  of  Tarrant  County 


23 


Adkins  and  Winton  (sp.  B);  H.  fremonti  Marcou  (sp.  C);  H. 
spp.  H-J. 

Kiamitia  Marl: 

**  Gryphea  navia  Hall. 

Gryphea  washitaensis  (lowest). 

Pholadomya  sp. 

♦Exogyra  plexa  Cragin  (highest). 

♦Schloenbachia  belknapi  Marcou  (highest). 

♦Fecten  irregularis  Boese  (highest). 

♦Schloenbachia  acutocarinata  Shumard  (highest). 

♦Exogyra  texana  Roemer  (highest). 

Cyprimeria  sp.  1. 

Fredericksburg  Division : 

Cyprimeria  sp.  1. 

*Schloenbachia  sp.  near  belknapi. 

Schloenbachia  acutocarinata  Shumard 
*Diplopodia  taffi.  Cragin. 

♦♦Coral  syndrome:  Parasmilia  sp.,  Trochosmilia  sp. 

♦Holectypus  sp. 

♦Enallaster  texanus  Roemer  (abundant). 

*Hemiaster  sp.  near  whitei  Clark. 

♦♦Salenia  mexicana.  Upper  level. 

Exogyra  plexa  Cragin  (small  form). 

** Syndrome  of  Chondrodonta  sp.  aft.  munsoni  (Hill),  Pecten  ir- 
regularis (Boese),  Cinulia,  Lima,  Pinna  sp.  near  comancheanus 
Cragin,  etc. 

*Engonoceras  sp.  aff.  pi'edernale  von  Buch. 

♦Exogyra  plexa  Cragin  (large  form). 

* *Schloenbachia  acutocarinata  (Shumard)  (abundant). 

Pholadomya  sancti-sabae  Roemer  (abundant). 

.Gryphea  maxcoui  Hill  and  Vaughan  (abundant). 

♦Schloenbachia  sp.  A. 

♦Gryphea  marcoui  (Upper  Conglomerate). 

Exogyra  texana  (Upper  Horizon,  abundant). 

Salenia  sp.  (lower  level). 

Protocardia  filosa  (Conrad). 

Cerithium  bosquense  Shumard. 

Natica  sp.  aff.  pedernalis  Roemer. 

Walnut  conglomerate  and  clay: 

♦Schloenbachia  acutocarinata  Shumard  (lowest) 

Enallaster  sp.,  Turritella  sp. 

♦Gryphea  marcoui  conglomerate. 

Paluxy  sands:  No  fossils  noted  in  Tarrant  County. 


24 


University  of  Texas  Bulletin 


THE  GEOLOGICAL  SECTION 


The  marine  formations  found  in  Tarrant  County,  as  already 
stated,  are  those  of  the  Cretaceous  System.  In  addition  there 
are  alluvial  and  terrace  deposits  of  the  Cenozoic.  In  the  fol- 
lowing table  these  formations  are  listed  in  order,  the  oldest 
foimations  being  placed  at  the  bottom  of  the  table.  In  the 
second  column  is  given  the  probable  equivalence  of  the  terms 
here  used  as  applied  to  other  sections  in  Central  Texas,  as  given 
in  Bulletin  44  of  the  Bureau  of  Economic  Geology.  Of  the 
formations  here  listed,  the  oldest  actually  exposed  at  the  surface 
in  Tarrant  County  is  the  Paluxy.  The  older  formations,  how- 
ever, are  penetrated  in  well  drilling. 


Table  OF  GEOLOGIC  FORMATIONS'  OF  TARRANT  COUNTY1 


Tarrant  County  Section. 

Cenozoic  and  Recent 

Eagleford  

Woodbine  

Gray  son  ) 

Mainstreet^ 

Pawpaw 

Weno 

Denton 

Fort  Worth  \ 

Duck  Creek  j 
Kiamitia  J 
Edwards  'j 

Comanche  Peak  l 

Goodland  J 

Walnut  

Paluxy 

Glen’ose  

Trinity 

Pennsylvanian 


Central  Texas 
Section. 

Cenozoic  and  Recent. 
Eagleford 
, Buda  ( ? ). 

.Del  Rio. 


Georgetown. 


Peak. 

Walnut. 

Paluxy. 

Glenrose. 

Travis  Peak. 


^Edwards. 

jComanche 


Tn  this  tabulated  statement  of  formations  the  Woodbine  of 
Northern  Texas  appears  as  the  equivalent  of  the  Buda  of  Central 
Texas.  Although  in  accordance  with  present  usage,  the  authors  wish 
to  express  reserve  with  regard  to  the  equivalence  of  the  Woodbine 
in  the  Central  .Texas  section. 


The  Geology  of  Tarrant  County  25 

DESCRIPTION  OF  FORMATIONS. 

PENNSYLVANIAN 

Knowledge  of  the  composition  and  exact  horizons  of  the 
Pennsylvanian  strata  beneath  Tarrant  County  is  very  defective 
and  awaits  further  drilling  and  especially  a careful  and  intelli- 
gent recording  cf  the  well  logs.  The  Tucker’s  Hill  well,  drilled 
in  East  Fort ‘Worth  in  1892.  apparently  penetrated  at  1120  feet 
a series  of  alternating  clays  and  sandstones;  the  ‘Polytechnic’ 
well  went  out  of  “dark  brown  shale  and  sand”  at  1200  feet;  the 
record  for  1200-1297  feet  is  missing ; 1297-1416  feet  is  recorded 
as  “blue  shale”.  From  logs  of  other  wells  it  is  known  that  the 
base  of  the  Trinity  is  red  sandstone  and  the  top  of  the  Pennsyl- 
vanian at  Fort  Worth  is  bluish  to  black  shales  so  that  the  parting 
between  the  Comanchean  and  the  Pennsylvanian  sediments  in 
the  Polytechnic  well  possibly  lay  in  the  gap  in  the  log,  sum- 
marized. above. 

DIP  OP  THE  PENNSYLVANIAN  ROCKS 

A contouring  of  the  basal  Trinity  does  not,  of  course,  give 
information  which  determines  the  attitude  of  the  underlying 
Paleozoic  rocks,  since  the  two  systems  are  unconformable. 
Well  data  show  an  eastward  dip  of  the  base  of  the  Trinity  sand, 
and  an  eastward  dip  of  the  underlying  Pennsylvanian  strata  has 
been  assumed.  In  addition  there  appears  to  be  a large  depres- 
sion, possibly  synclinal,  in  the  Pre-Comanchean  strata  under 
Tarrant  County.  (See  page  97). 

COMANCHEAN 

TRINITY  DIVISION1 

The  Trinity  Division  consists  in  Tarrant  County  of  the  fol- 
lowing formations,  beginning  at  the  bottom:  Trinity  (Base- 

ment) sands,  Glenrose  limestone,  Paluxy  Sands.  The  Basement 
sands  are  underlain  by  the  Pennsylvanian,  and  the  Paluxy 

Hn  this  paper  we  follow  the  terminology  of  Hill,  who  established 
the  accepted  classification  of  the  Texas  Comanchean  and  mimed  its 
divisions  and  formations. 


26 


University  of  Texas  Bulletin 


sands  are  overlain  by  the  Walnut  formation  of  the  Fredericks- 
burg Division  of  the  Comanchean. 

TRINITY  (BASEMENT)  SANDS. 

The  Trinity  (Basement)  sand,  not  exposed  at  the  surface  in 
Tarrant  County,  is  an  important  reservoir  for  artesian  water 
under  the  Black  and  Grand  Prairies,  as  fully  explained  by  Hill. 
It  contains  at  least  three  important  artesian  levels  under  this 
area  and  is  probably  about  120  feet  thick.  Underneath  Fort 
Worth  it  is  penetrated  at  the  depths  of  from  1025  to  1150  feet. 

GLENROSE  LIMESTONE. 

Proceeding  southward  from  southern  Oklahoma,  the  Antlers 
or  basal  Cretaceous  sand,  is  described  as  being  split  into  two 
sandy  formations  by  an  intervening  wedge-shaped  limestone  mass 
which  thus  occupies  a place  between  the  two  sands.  It  increases 
in  thickness  southeastward.  This  limestone  is  the  Glenrose 
formation.  It  is  not  exposed  at  the  surface  in  Tarrant  County, 
but  has  been  penetrated  by  wells  at  various  points  in  the  county. 
It  is  stated  by  Hill  to  be  about  470  feet  thick  under  Fort  Worth 
and  to  increase  in  thickness  southeastward  at  the  rate  of  8 or  9 
feet  per  mile.  Underneath  Fort  Worth  it  occurs  at  depths  of 
about  500-1025  feet. 

PALUXY  SANDS. 

This  sand,  the  westernmost  outcropping  formation  in  the 
county,  is  exposed  in  the  valley  of  the  West  Fork,  in  the  north- 
west corner  of  the  county.  It  is  an  artesian  water  reservoir  and 
consists  of  alternating  layers  of  rather  unconsolidated  sands  and 
compact  clay,  the  formation  being  iron-stained  but  free  from 
gypsum,  and  its  water  of  a correspondingly  good  quality.  On 
exposure  -the  material  is  seen  to  be  poorly  consolidated,  and 
readily  disintegrated;  it  contains  rounded  concretions  and  phos- 
phate nodules.  The  Paluxy  sand  is  about  100  feet  thick  and 
contains  three  principal  artesian  layers.  It  is  poor  in  fossils. 

FREDERICKSBURG  DIVISION. 

The  Fredericksburg  division  consists  in  north-central  Texas 


The  Geology  of  Tarrant  County 


27 


of  four  groups  of  strata : Edwards  limestone,  Comanche  Peak 
limestone,  Goodland  limestone,  and  Walnut  shell  conglomerate 
and  clays.  Since  the  limits  of  each  of  these  divisions  are  still 
being  studied,  the  formations  will  be  discussed  together. 

Brief  Diagnosis : Underlying  the  narrow  but  very  easily 

recognizable  outcrop  of  brownish  shelly  Kiamitia  marl  in  Tar- 
rant County  is  117  feet  of  white,  chalky,  rather  pure  limestone 
and  interbedded  whitish  marl,  which  makes  the  bluffs  of  the 
Clear  Pork  between  Port  Worth  and  Benbrook,  and  is  exposed 
over  a considerable  area  along  the  two  forks  of  the  Trinity. 
Beneath  this  whiter  rock  is  a bluish  shell  conglomerate  which  is 
the  top  of  the  Walnut  formation.  Under  the  conglomerate  is  a 
series  of  marls,  unconsolidated  sand  and  shell  conglomerates  ex- 
tending about  100  feet  down  to  the  easily  recognized  Paluxy 
sand.  A characteristic  sequence  of  fossils  in  these  sediments  is 
noted  in  the  following  discussion. 

Lithology:  The  upper  16  feet  of  the  Fredericksburg  Division 
at  Port  Worth  is  a hard,  resistant,  crystalline,  rather  unfossilif- 
erous  limestone  which  forms  a protective  cap  for  the  underlying, 
more  chalky  limestones.  This  has  been  considered  the  northern 
attenuated  portion  of  the  Edwards  and  Comanche  Peak  forma- 
tions, which  thicken  rapidly  toward  the  south,  forming  below 
the  Brazos  the  substratum  of  the  Lampasas  Cut-  Plain.  Tat! 
records  from  Benbrook  a rudistid  in  the  upper  four  feet  of  the 
Fredericksburg;  these  fossils  and  an  abundance  cf  flinty  masses 
characterize  the  Edwards  limestone  farther  south. 

Below  the  upper  16  feet  is  a series  of  softer,  chalky  limestones 
and  light  straw-colored  marls  extending  from  a point  which 
will  be  defined  as  the  top  occurrence  of  Schloenbachia  sp.  aff. 
belknapi  Marcou,  downward  to  the  top  of  a prominent  blackish- 
blue,  hard  shell  conglomerate  made  almost  entirely  of  the  oyster 
Gryphea  marcoui  Hill  and  Vaughan.  This  conglomerate  lies 
117  feet  below  the  base  of  the  Kiamitia  marl,  the  Fredericksburg- 
Washita  contact,  which  is  easily  recognized  in  Tarrant  County. 
The  basal  part  of  the  limestone  above  the  conglomerate  contains 
considerable  yellowish-brown  marl.  The  basal  contact  is  sharply 
defined.  The  limestone  contains  a characteristic  sequence  of 


28 


University  of  Texas  Bulletin 


fossils,  which  is  invariable  over  a wide  area.  These  fossils  are, 
in  part,  beginning  at  the  top : — 

1.  Schloenbachia  sp.  near  belknapi  (Marcou). 

2.  Schloenbachia  acutocarinata  (Shumard). 

3.  Diplopodia  taffi  Cragin. 

4.  Coral  syndrome:  Paiasmilia,  Trochosmilia. 

5.  Holectypus  sp. 

6.  Enallaster  texanus  Roemer. 

7.  Hemiaster  sp.  near  whitei  Clark. 

8.  Salenia  mexicana.  Upper  level. 

9.  Exogyra  plexa  Cragin.  Small  form. 

10.  Syndrome  of  Chondrodonta  sp.  aff.  munsoni  (Fill),  Lima, 

Pecten  irregularis  Boese. 

11.  Engonoceras  sp. 

12.  Schloenbachia  acutocarinata  (Shumard),  abundant. 

13.  Pholadomya  sancti-sabae  Roemer,  abundant. 

14.  Gryphea  marcoui  Hill  and  Vaughan,  abundant. 

15.  Schloenbachia  sp. 

16.  Schloenbachia  sp.  (6"). 

17.  Turritella  sp.,  abundant. 

18.  Gryphea  marcoui.  Upper  conglomerate. 

19.  Exogyra  texana,  Upper  horizon,  abundant. 

20.  Salenia  sp.,  Lower  level. 

21.  Protocardia  filosa  Conrad. 

2 2.  Natica  pedernalis  Roemer. 

The  foregoing  white  limestone  portion  of  the  Fredericksburg 
Division  is  exposed  in  a vertical  section  at  the  north  end  of  the 
Lake  Worth  dam;  good  exposures  occur  on  the  Azle  road  9 
miles  northwest  of  Fort  Worth,  where  practically  the  whole 
thickness  is  seen  underlying  a nearly  complete  section  of  the 
Kiamitia  marl  ; on  the  Stove  Foundry  road,  half  way  between 
Fort  Worth  and  Benbrook,  where  the  upper  third  is  well  ex- 
posed; on  the  Weatherford,  Granbury,  and  Plover  roads;  and 
elsewhere  in  the  area  mapped.  The  formation  is  very  fossilifer- 
ous,  most  of  the  fossils  being  mud  casts. 

The  cut  in  the  hill  at  the  north  end  of  the  Lake  Worth  dam 
sections  the  upper  part  of  the  Fredericksburg  division,  com- 
monly assigned  to  the  Goodland  limestone,  and  continues  down- 
wards to  the  top  of  the  bluish-gray  Walnut  shell  conglomerate. 


The  Geology  of  Tarrant  County 


29 


LAKE  WORTH  SECTION  OF  THE  FREDERICKSBURG  DIVISION 

Feet.  Inches. 

Duck  Creek  Limestone  40 

(The  lower  two  feet  of  this  limestone  is  the  Hamites 
ledge.) 

Kiamitia  marl:  Brown  marl  containing  Gryphea  navia 

and  Exogyra  plexa,  forming  grassy  slope  above  cliff.  .31  6 


Fredricksburg  Division: 

9.  Chalky  limestone,  sparsely  fossiliferous 26  9 

This  contains  the  following  strata: 

9h.  Massive  limestone  in  4 layers 6 feet. 

9g.  Marly  fragmented  limestone 8 

9f.  Blue  marl  1 

9e.  Three  marl  layers  interbedded  with 

thin  limestone  layers 3 

9d.  Fragmented  limestone  4 

• 9c.  Blue  marl  with  2 limy  layers 2 

9b.  Chalky  limestone.  Echinoid  zone.  ...  2 

9a.  Blue  marl 0.75 

These  strata  are  rather  barren  in  the  upper  16  feat 


but  contain  especially  in  the  lower  part:  Hemiaster 
whitei,  Enallaster  texanus,  Diplopodia  taffi, 
Schloenbachia  sp.  aff.  belknapi,  S.  acutocarinata, 

Cinulia,  Lima,  Pecten  irregularis,  Gryphea  mar- 
coui,  Exogyra  texana,  Pinna  sp.  aff.  comancheanus, 

Cyprimeria,  Lunatia,  Parasmilia,  Trochosmilia  and 
many  other  fossils. 

8.  Massive  chalky  limestone 5 3 

This  massive  and  distinct  band  contains: 

Hemiaster  whitei,  Lima  wacoensis,  Lima  sp,  Enal- 
laster texanus,  Pecten  subalpina,  P.  irregularis, 

Exogyra  texana,  E.  plexa,  Engonoceras,  Schloen- 
bachia acutocarinata,  S.  sp.  aff.  belknapi,  Tylos- 
toma  sp. 

7.  Blue  calcareous  marl 5 6 

This  distinct  marl  band  is  conspicuous  (Plate  1), 
and  contains:  Turritella,  Pholadomya,  Lima, 

Trigonia,  Cyprimeria,  Exogyra  plexa,  Enallaster 
texanus. 

6.  Massive  chalky  limestone 13  0 

Hemiaster  whitei,  Hemiaster  sp,  Gryphea  marcoui, 

Lima  wacoensis,  Schloenbachia  acutocarinata, 
sheets  of  celestite. 


30  University  of  Texas  Bulletin 

Feet.  Inches. 

5.  Blue  marl  7 0 


Hemiaster,  Lima,  Pecten  irregularis,  Enallaster 
texanus  and  many  other  fossils. 

4.  Chalky  limestone  10  0 

The  bottom  of  this  layer  is  about  at  the  level  of  the 
approach  to  the  dam. 

3.  Massive  impure  fragmented  chalky  limestone,  marly 

at  the  base 43  0 

1.  Massive  chalky  limestone  overlying  the  Walnut  shell 
conglomerate  and  seen  in  the  channel  below  the 
dam 5 0 


Total 117  0 

Walnut  Conglomerate: 

Massive  blue  gray  shell  conglomerate  composed  mainlj 

of  Gryphea  marcoui  shells 5 0 

The  Fredericksburg  limestone  can  be  studied  to  advantage 
on  the  steep  slopes  of  the  valley  of  the  West  Fork,  just  north- 
east of  the  Lake  Worth  dam,  where  its  fossil  sequence  is  excel- 
lently displayed.  The  following  series  of  levels  holds  for  any 
locality  in  Tarrant  County  within  narrow  limits,  and  may  be 
used  at  Lake  Worth,  Mary’s  Creek  north  of  Benbrook,  Bear 
Creek  southwest  of  Benbrook,  Azle  Road  sections  northwest  of 
Fort  Worth,  and  Stove  Foundry  Road  sections  along  the  Texas 
and  Pacific  track  between  Fort  Worth  and  Benbrook. 


DISTANCE  OF  FREDERICKSBURG  FOSSIL  HORIZONS  AND  ZONES  OF 
ABUNDANCE  BELOW  THE  TOP  OF  THE  FREDERICKSBURG 
LIMESTONE,  IN  TARRANT  COUNTY 

Feet. 


Fossils  sparse 

Corals:  Parasmilia,  Trochosmilia 

Diplopodia 

Salenia  (upper  level) 

Trichotropis  shumardi 

Exogyra  plexa  

Lima  (abundant)  

Ostrea  sp.  aff.  munsoni 

Schloenbachia  belknapi  

Hemiaster  sp.  (small) 

Salenia  (lower  level) 

Protocardia  filosa 

Exogyra  texana  

Natica  pedernalis  


0-16 

23 

24 

26 

27 

28 

28 

28 

40 

36 

55 

57 

40-57;  90-100 
110 


1.  Columnar  section  of  the  Fredericksburg  limestone  in  the 
valley  of  the  West  Fork  of  the  Trinity  River  near  the  Lake 
Worth  Dam.  The  upper  half  of  the  section  is  seen  in  Plate  1. 
The  numbers  refer  to  corresponding  strata  described  on  pp. 
29-32.  Vertical  scale,  y8  inch=l  foot. 


32 


University  of  Texas  Bulletin 


The  portion  of  the  Fredericksburg  Division  lying  between 
the  limestone  just  described  and  the  Paluxy  sand  below,  consists 
of  alternating  conglomerate  and  sand  layers  totalling  about  100 
feet  iu  thickness.  This  series  of  strata  constitutes  the  prom- 
inent escarpment  seen  below  the  Fredericksburg  limestone  on 
the  Azle  road,  two  miles  east  of  Azle,  on  the  Weatherford  road 
near  the  county  line,  and  elsewhere  in  the  northwest  corner  of 
Tarrant  County.  The  topmost  impervious  conglomerate  pro- 
tects the  underlying  unconsolidated  sands  from  weathering,  and 
thus  gives  to  the  whole  escarpment  a resistant  appearance.  In 
fact  the  cap  conglomerate  breaks  off  and  strews  the  sides  of 
the  hills  with  fossiliferous  slabs  and  debris.  This  topmost  layer 
sometimes  weathers  unevenly,  and  small  hard  caps  remain, 
forming  the  Walnut  peaks  seen  near  Azle.  The  shell  conglom- 
erate outcrops  around  Lake  Worth,  where  it  is  seen  at  the  small 
exposure  just  below  the  dam  and  for  several  miles  up  the  river. 
This  basal  Fredericksburg  belongs  to  the  Walnut  formation,  but 
the  upper  contact  will  not  be  defined  here. 


SECTION  OF  THE  LOWER  PORTION  OF  THE  FREDERICKSBURG 
DIVISION,  ON  AZLE  ROAD,  TWO  MILES  EAST  OF  AZLE 
TARRANT  COUNTY,  TEXAS 


Thickness 
in  feet. 


Brown  limy  marl  with  Gryphea  marcoui,  Turritella,  Exogyra 

texana,  Enallaster,  Natica 20 

Blue-black  shell  conglomerate,  containing  Gryphea  marcoui  (in 
great  numbers),  Trigonia,  Pecten  subalpina,  Pecten  sp., 
Exogyra  texana  and  spp.,  Cyprimeria,  Turritella,  Enallaster 

texanus,  Remondia  (?),  Lunatia  sp 5 

Unconsolidated  sand,  slightly  yellow  stained,  containing  ferrugi- 
nous fragments.  No  fossils  noted 7 5 

Arenaceous  reddish  limestone  and  shell  conglomerate,  contain- 
ing Gryphea  marcoui,  Turritella  sp.,  Enallaster  texanus, 

Exogyra  texana  25 

Paluxy  sand. 


The  upper  conglomerate  of  the  Walnut,  a mass  of  Gryphea 
marcoui  shells,  is  seen  in  the  east  bank  of  Lake  Worth  at  the 
Nine-mile  bridge,  just  opposite  the  bathing  beach.  It  should 
be  especially  noted  that  there  is  another  conglomerate  having 
the  same  sequence  of  lithology  and  of  fossils,  lying  stratigraphi- 
callv  20  feet  above  this  level  and  easily  confused  with  it. 


The  Geology  of  Tarrant  County 


33 


FAUNA  OF  THE  GOODLAND  LIMESTONE 


Hemiaster  whitei  Clark 
Hemiaster  sp. 

Enallaster  texanus  (Roemer) 
Holectypus  planatus  Roemer 
Salenia  mexicana  S'chlueter 
Diplopodia  taffi  Cragin 
Cypho.soma"  texana 
Goniopygus  sp. 

Engonoceras  sp. 

S’chloenbachia  spp. 

Schloenbachia  acutocarinata 
S'numard) 

Turritella  seriatim-granulosa 
Roemer 
Turritella  sp. 

Cinulia  tarrantensis  Cragin 
Trichotropis  shumardi  Cragin 
Cylindrites  formosus  Cragin 
Cerithium  bosquense  Shumard 
Tylo.stoma  chihuahuense  Boese 
Tylostoma  tumidum?  S’humard 
Lunatia  pedernalis  Roemer 
Nerinea  sp. 

Neritina  sp. 

Rostellaria  subfusiformis  Conrad 


Turbo  sp. 

Homomya  sp. 

Pinna  sp.  aff.  comancheanus 
(Cragin) 

Protocardia  texana  (Conrad 
Protocardia  filosa  (Conrad) 
Isocardia  sp. 

Oyprimeria  texana  (Roemer) 
Pecten  occidentalis  ? (Conrad) 
Pecten  irregularis  (Boese) 

Pecten  subalpina  Boese) 
Exogyra  texana  Roemer 
Exogyra  plexa  Cragin  (Boese) 
Exogyra  sp.  aff.  plexa  Boese 
Gryphea  marcoui  Hill  & Vaughan 
Pholadomya  sancti-sabae  Roemer 
Ostrea  sp.  aff.  johannae  Choffat 
Lima  wacoensis  Roemer 
Trigonia  sp. 

Tapes  sp. 

Corbula  sp. 

Schloenbachia  sp.  aff.  belknapi 
(Marcou) 
crustacean  claws 
Trochosmilia  texana  (Conrad) 
Parasmilia  austinensis  Roemer 


FAUNA  OF  THE  WALNUT  FORMATION. 


Exogyra  texana  Roemer 
Exogyra  weatherfordensis  Cragin 
Enallaster  texanus  (Roemer) 
Remondia  ? sp. 

Gryphea  marcoui  Hill  & Vaugban 
Salenia  sp.  aff.  mexicana 


Turritella  sp. 

Pecten  irregularis  (Boese) 
Triginia  sp. 

Schloenbachia  acutocarinata 
(Shumard) 

Holectypus  sp.  aff.  planatus 


WASHITA  DIVISION 


The  Washita  Division  of  the  Comanchean  Cretaceous  is  very 
fully  developed  in  Tarrant  County,  and  includes  the  following 
formations  beginning  at  the  base : Kiamitia,  Duck  Creek,  Fort 
Worth,  Denton,  Weno,  Pawpaw,  Mainstreet,  Grayson,  and 
Woodbine.1 

KIAMITIA  MARL 

Brief  Diagnosis : The  Kiamitia  formation  is  a brownish  yel- 
low, slightly  calcareous  marl,  with  scattered  limestone,  shelly 
and  flaggy  bands  and  abundant  deposits  of  oyster  shells,  mostly 
Gryphea  navia.  It  is  27  feet  thick  at  Fort  Worth.  It  weathers 
out  usually  into  a narrow  hillside  slope  which  lies  above  the 
glaring  white  Fredericksburg  limestone  and  below  the  scarp 
produced  by  the  basal  Duck  Creek  limestone.  The  outcrops  are 

*The  inclusion  of  the  Woodbine  in  the  Washita  Division  is  tenta- 
tive on  the  part  of  the  authors. 


3— Tarrant 


34 


University  of  Texas  Bulletin 


usually  grassy  and  poorly  exposed,  and  due  to  their  situation 
are  often  contaminated  by  gravel  deposits.  The  limits  of  the 
formation  are  sharply  defined  in  Tarrant  County. 

Description  of  Localities : This  formation  skirts  the  western 
edge  of  the  Black  Prairie  at  the  foot  of  its  escarpment  and 
forms  a narrow  sloping  strip  often  less  than  50  feet  wide.  Due 
to  its  narrowness  and  to  the  close  affinities  of  the  formation 
with  the  Fredericksburg  strata  (page  27)  it  has  not  been  sep- 
arately mapped ; but  it  may  be  projected  on  the  map  by  cutting 
off  a hair-line  strip  from  the  east  border  of  the  Fredericksburg 
Division  as  mapped.  The  formation  decreases  in  thickness  and 
in  shelliness  southward.  At  Shawnee  Creek,  Denison,  it  is  over 
60  feet  thick  and  has  prominent  bands  of  hard  shell  conglom- 
erate distributed  through  most  of  its  thickness.  In  Tarrant 
County  the  shell  bands  have  disappeared  and  the  shells  are  pres- 
ent in  smaller  amounts  in  the  loose  limy  layers  and  the  interbed- 
ded  marls.  On  the  Noland’s  River,  southeast  of  Blum,  the  forma- 
tion is  19  feet  thick  and  very  similar  to  its  outcrops  in  Tarrant 
County.  The  constant  features,  from  the  Red  River  to  the 
Brazos,  according  to  Hill,  are  a basal  member  which  is  cal- 
careous and  argillaceous  and  contains  quantities  of  shell  frag- 
ments ; the  upper  part  of  the  formation  is  a series  of  calcareous 
laminated  blue  clays  which  turn  brownish-black  upon  weath- 
ering, interstratified  layers  of  indurated  calcareous  clay  (e.  g., 
stratum  15  below)  and  laminated  sandstone  flags  (strata  2,  4, 
7,  17).  The  flags  are  somewhat  calcareous  and  the  whole  forma- 
tion shows  iron  discoloration.  South  of  the  Brazos  the  forma- 
tion is  attenuated,  and  near  Round  Rock  is  stated  to  be  an 
“earthy,  blue,  marly,  rather  hard  limestone”  at  the  base  of 
the  Georgetown  limestone.  (Hill). 

In  Tarrant  County  there  are  two  general  types  of  Kiamitia 
exposure,  the  hillside  and  the  upland  type,  of  which  the  latter 
is  very  rare  and  exceptional.  If  the  overlying  Duck  Creek  lime- 
stone has  been  leveled  or  brought  to  a very  gentle  grade  over  a 
considerable  area,  the  Kiamitia  will  form  a gentle  slope  back- 
ward from  the  resistant  underlyiug  Fredericksburg  rocks  and 
will  produce  the  upland  type  of  exposure.  This  sort  of  outcrop 
is  seen  at  the  western  edge  of  Duck  Creek  uplands,  hence  its 


The  Geology  of  Tarrant  County 


35 


rarity.  The  best  examples  are  along  the  Azle  road  near  Lake 
Worth.  On  the  prevailing  hillside  outcrops  exposures  are  pro- 
duced in  stream  cuttings  but  they  are  very  inconsecutive.  The 
exposures  lying  near  the  main  drainage  lines  are  usually  partly 
overlain  by  terrace  gravel  deposits.  However,  the  present  day 
lateral  drainage  is  rapidly  cutting  into  the  uplands  and  the 
headwaters  of  these  valleys  show  uncontaminated  Kiamitia 
exposures. 

Nearly  a complete  exposure,  lacking  the  upper  contact,  is 
seen  on  the  Azle  road,  about  6 miles  northwest  of  Fort  Worth 
and  2 y2  miles  northeast  of  Lake  Worth,  at  the  point  where  the 
road  sections  the  Kiamitia  marl  and  passes  down  thru  the  Good- 
land  escarpment. 


SECTION  OF  KIAMITIA  MARL,  AZLE  ROAD,  SIX  MILES  NORTHWEST 
OF  FORT  WORTH 


18-19 

17 

16 

15 

14 

13 

12 

11 

10 

9 

8 

7 

5-6 

4 

3 

2 

1 

A' 


Height  from  Thickness 

bottom  of 

section  Feet  In. 

From 

Brown  marl.  Gryphea  navia  ...  .20' 

Hard  shelly  limestone . ..19'9" 

Very  fossiliferous  bluish  marl  “E. 

plexa  zone”  T 19' 

Fractured  limestone,  double  band 

with  central  marl  layer 18' 

Bluish  fossiliferous  marl 16' 

Hard  coarse  grained  limestone, 

blue  upon  fracture  14'4" 

Blue  marl  14' 

Hard  shelly  limestone 13'6" 

Blue  marl  13' 

Blue  shaly  marl 12'10" 

Brownish  marl,  bluish  before 

weathering  . 12' 

Brown  sandy  flag ll'lO" 

Blue  marl,  more  compressed  at  top  6 '6" 

Light  colored  soft  sandy  flag.  . . . 6'4" 

Blue  marl  5' 

Light  colored  soft  sandy  flag.  . . . 4'10" 

Brown  laminated  clayey  marl, 

blue  on  fresh  exposure 

Fredericksburg  limestone. 

(Upper  2 feet  of  Kiamitia  concealed  by  soil  overwash). 


To 

25' 

20' 

19'9" 

19' 

18' 

16' 

15'4" 

14' 

13'6" 

13' 

12'10" 

ll'lO" 

6'6" 

6'4" 

5' 

4'10" 


8 

4 

6 

6 

2 

10 

2 

4 

2 

4 

2 

10 


36 


University  of  Texas  Bulletin 


These  several  members  in  the  Azle  section  may  be  arranged 
in  three  groups  that  can  be  distinguished  and  described  as 
below : 


18-19 


17 

Ife 

15 

r* 

13 

\Z 
1 1 

'§ 

8 

7 

5-6 


4- 

3 

2 


Fig.  2.  Columnar  section  of  the  Kiamitia  formation  in  cut  on 
Azle  road,  eight  miles  northwest  of  Fort  Worth.  The  numbers 
refer  to  corresponding  strata  described  on  pp.  35-7.  Vertical 
scale,  V8  inch  — = 1 foot. 

Basal  portion  ( strata  1-6)  : Approximately  the  lower  half 
of  the  formation  is  a clay-marl  which  is  bluish  or  bituminous 
on  fresh  exposure  and  extensively  laminated;  is  brown  on 
weathering,  breaks  into  cuboidal  chunks,  indurates  locally  in 
thin  layers,  and  at  places  is  sandy.  Hill  notes  the  following 
features  of  this  portion : It  is  a dark  blue  clay  resting  directly 
upon  the  smooth  surface  of  the  white  Fredericksburg  limestone; 
at  a level  of  5 feet  above  the  base  is  a persistent  band  of  gray 
indurated  limy  clay  (2)  ; at  places  it  is  variably  arenaceous  in 
the  basal  portion  and  some  layers  very  near  the  base  are  sandy ; 
near  Aledo  (Parker  County)  there  is  a basal  layer  of  laminated, 
sandy,  very  calcareous  and  argillaceous  material  which  contains 


The  Geology  of  Tarrant  County 


37 


large  quantities  of  shell  fragments.  This  argillaceous  portion 
at  the  Brazos  is  not  more  than  5 feet  thick. 

The  Fredericksburg-Kiamitia  contact  is  lithologically  the 
most  contrasting  and  abrupt  change  in  the  series.  It  is  seen 
to  advantage  at  the  Marine  Creek  crossing  of  the  Azle  Road. 
Here  the  blue,  closely  laminated,  flaky  Kiamitia  marl  lies  directly 
upon  the  flat  but  irregular  and  lumpy  surface  of  the  limestone. 
In  stream  cuts  the  marl  may  be  removed  exposing  the  limestone. 
At  localities  nearer  Fort  Worth  a finely  fragmental  shell  de- 
posit was  noted  just  over  this  limestone;  and  at  the  Texas 
Pacific  Railroad  crossing  of  the  Clear  Fork  is  a six  inch  slightly 
shelly,  blue  marl  stratum  at  the  base  of  the  Kiamitia.  As  noted 
later  the  fossils  are  mainly  continuous  across  this  contact. 

Middle  portion  ( strata  7-17)  : This  limestone  portion  is 

topographically  and  paleontologically  the  most  interesting  part 
of  the  formation.  It  consists  of  six  thin  limestone  layers  or 
flaggy,  sandy  layers,  alternating  with  blue  and  brown  calcareous, 
laminated,  and  in  part  carbonaceous,  clay.  Three  of  these  layers 
(7,  9,  17)  are  calcareous  sandstone  flag  layers  each  2 or  3 inches 
thick;  of  the  other  three  layers  13  is  a hard,  coarse-grained 
limestone,  11  and  15  are  soft  marly-chalky  limestones.  All  of 
the  layers  are  fossiliferous,  and  the  formation,  in  richness  of 
fossils,  is  quite  the  reverse  of  the  description  of  Taff.  The  faun# 
is,  however,  poor  in  ammonites  and  echinoids. 

Upper  portion  ( strata  18-19)  : This  is  a clay  marl,  brown, 

non-laminated  and  sparsely  shelly,  without  the  extensive  con- 
glomerate sheets  which  are  so  prominent  in  the  upper  Kiamitia 
of  the  Red  River  section.  Gryphea  navia  and  G.  corrugata 
were  noted  in  this  portion. 

Palentology : Although  the  Kiamitia  formation  has  been  placed 
in  the  Washita  division  it  has  strong  paleontological  affinities 
with  the  Fredericksburg,  as  shown  by  the  following  table: 


38 


University  of  Texas  Bulletin 


Fossils'  of  the  Kiamitia 
marl,  at  Fort  Worth, 
Texas. 


Formation  or  formations  in  which 
fossil  is  found,  indicated  by  aster- 
isk in  column  opposite  fossil 
named. 

Fredericks-  Kiamitia  Duck  Washita 


burg 

Gryphea  navia  Hall 
Avicula  leveretti  Cragin 
Schloenbachia  sp.  (belknapi?) 
Ostrea  sp. 

Exogyra  texana  Roemer  * 

Pecten  irregularis  Boese  * 

Exogyra  plexa  Cragin  * 

Schloenbachia  acutocarinata 
Shumard  * 

Isocardia  sp.  * 

Homomya  sp.  * 

Trigonia  sp.  * * 

Pecten  subalpina  ? Boese  * 

Protocardia  texana  (Conrad)  * 
Cyprimeria  sp.  * 

Gryphea  washitaensis  Hill 
Gryphea  corrugata  Say 


Creek 


Kiamitia  Fauna 

(Forms  known  to  occur  only  in  the  Kiamitia) 


Members  of  Azle  section 
preceding,  in  which  fossil 
is  found 


Pinna  sp 3 

Gryphea  navia  Hall  1-19 


The  typical  G,  navia  is  very  abundant  in  the  middle  third  of 
the  formation  at  Fort  Worth,  though  it  forms  thick  conglom- 
erates in  the  upper  portion  on  the  Red  River.  It  is  a massive 
imbricated  shell,  usually  with  a twisted  beak. 

Schloenbachia  acutocarinata,  Exogyra  plexa  (plicate  and 
non-plicate  forms),  and  Pecten  irregularis  were  not  seen  above 
the  stratum  16.  Exogyra  plexa  is  limited  to  this  layer. 

“16”  is  a very  fossiliferous  layer.  Below  it  the  fossils  de- 
crease in  number  and  in  the  lower  third  of  the  formation  are 
rare.  Schloenbachia  acutocarinata  and  Exogyra  texana  were 
not  observed  in  the  basal  Duck  Creek  limestone  as  at  the  Red 
River. 


The  Geology  of  Tarrant  County 


39 


DUCK  CREEK  FORMATION. 

The  Duck  Creek  formation  at  Fort  Worth  is  divisible  into  four 
lithological  and  palentological  members  beginning  at  the  top: 

(1)  Kingena  member — the  Duck  Creek  Marl. 

(2)  Scaphites  member — the  Duck  Creek  Limy  Marl. 

(3)  Schloenbachia  sp.  (aff.  trinodosa)  member, — the  Duck  Creek 
Marly  Lime. 

(4)  Desmoceras  member — the  Duck  Creek  Limestone. 

DUCK  CREEK  MARL  AND  LIMY  MARL 

These  groups  in  Tarrant  County  consist  of  a series  of  pre- 
vailingly light  colored  yellowish-gray  marls  containing  thin 
seams  of  impure  fragmental  chalky  limestone.  The  marl  is 
recognizable  in  the  landscape  as  a gently  sloping  shelf  or  terrace 
lying  at  the  base  of  the  escarpment  produced  by  the  overlying 
Fort  Worth  limestone  and  sloping  to  the  outcrop  of  a lime- 
stone  layer  which  lies  at  the  base  of  the  Marl  (stratum  17).  Be- 
low this  layer,  which  in  stream  cuts  forms  the  edge  of  the  marl* 
shelf,  the  slope  is  steep  and  is  continuous  with  that  the  the  Duck 
Creek  limestone  escarpment  below.  The  top  of  the  Duck  Creek 
limestone  is  a persistent  grayish,  usually  lichen-incrusted  band, 
Outcropping  below  the  edge  of  the  shelf  in  the  face  of  the  es- 
carpment. The  outcrop  of  these  strata  is  generally  narrow  and 
lies  along  the  rim  of  the  main  escarpment  as  seen  near  the  Texas 
Christian  University  at  Fort  Worth,  and  therefore  its  soil  value 
is  almost  negligible.  At  places,  however,  it  weathers  into  a 
brownish-yellow  hillside  slope  devoid  of  rock  and  is  then  indis- 
tinguishable from  the  Fort  Worth  upland  except  for  a slight 
topographic  break  at  their  junction.  The  series  is  34%  feet 
thick  near  Fort  Worth.  It  is  characterized  by  the  following 
well  defined  sequence  of  fossils: 

Pleurotomaria  austinensis  zone 

Upper  Kingena  zone 

Pecten  wrightii  zone 

Upper  Gastropod  horizon Globiconcha  (?),  Turritella, 

Diplopodia  zone  Fusus,  Cerithium 

Lower  (Main)  Kingena  zone 
Goniophorus  sp.  zone 

Crania  sp.  zone 

Limonite  fossil  (Lower  Gasteropod)  zone,  Scaphites  sp  B (top) 

Gerontic  Ammonite  zone Hamites  spp. 

Pinna  sp. 


40 


University  of  Texas  Bulletin 


Description  of  Localities:  The  Duck  Creek  Marl  and  Limy 
Marl  are  distinct  from  the  overlying  Fort  Worth  limestone  and 
the  underlying  Duck  Creek  limestone,  both  lithologically  and 
paleontologically,  and  have  as  much  justification  for  ranking  as 
a separate  formation  as  either  of  them.  If  they  are  to  be  placed 
with  either  it  should  be  with  the  Fort  Worth  limestone,  since 
fft fie  faunal  changes  are  very  abrupt  at  the  end  of  the  Duck 
dreek  limestone, 

The  Fort  Worth-Duck  Creek  contact  as  here  described  and 
mapped,  following  the  most  frequent  usage  in  the  literature,  is 
totally  arbitrary.  It  is  debatable  if  it  would  not  be  much  better 
to  place  this  contact  below  the  abundant  Kingena  zone  and  the 
horizon  of  Pecten  bellula  or  lower,  so  as  to  partition  the  ammon- 
ites and  echinoids  more  accurately.  Such  a contact  would  be  as 
well  warranted  lithologically  and  topographically  as  the  present 
one,  and  more  consistent  paleontologically;  but  since  the  forma- 
tions are  of  only  local  application,  no  insistence  is  placed  on  this 
matter  of  contact.  There  is  a clear  and  mappable  topographic 
break  above  the  stratum  24,  so  that  the  overlying  Fort  Worth 
limestone,  even  if  thin,  makes  a continuous  miniature  escarp- 
ment in  the  landscape.  The  only  other  consistent  topographic 
break  is  at  stratum  17,  which  is  resistent  to  erosion  and  caps 
the  underlying  Duck  Creek  escarpment;  17  forms  conspicuous 
horseshoe  bend  outcrops  in  runs,  while  24  fails  to  withstand 
erosion.  In  this  group  of  strata  the  limestone  beds  are  soft, 
chalky  and  fractured,  and  the  marls  are  yellowish,  water-bear- 
ing and  very  calcareous.  Due  to  the  thinness  and  softness  of 
the  limestone  bands  these  degrade  rapidly  and  so  produce  no 
conspicuous  surface  features.  Only  the  Duck  Creek  stratum  21 
is  noticeably  sandy  and  flaggy.  The  limestones  and  marls  grade 
into  each  other,  and  locally  there  is  slight  lateral  replacement. 

The  Duck  Creek  marl  is  typically  exposed  in  the  run  above 
the  first  turn  of  the  street  car  track  north  of  Texas  Christian 
University,  and  in  the  cut  of  the  military  road  nearby. 


Fig.  3.  Columnar  section  of  the  Duck  Creek  formation  in  cuts 
near  Forest  Park,  Fort  Worth.  The  numbers  refer  to  cor- 
responding strata  described  on  pp.  42-4.  Vertical  scale, 
Vs  inch  — 1 foot. 


42 


TJmversity  of  Texas  Bulletin 


SECTION  OF  THE  DUCK  CREEK  MARL,  ON  BOTH  SIDES  OF 
RUN  SOUTHEAST  OF  FIRST  TURN  OF  STREET  CAR 
TRACK,  % MILE  NORTH  OF  TEXAS  CHRISTIAN  UNI- 
VERSITY AND  3 Yz  MILES  SOUTHWEST  OF  FORT  WORTH. 

Altitude  of  top  of  Duck  Creek  Marl  680  feet. 

Thickness 
Feet  Inches 

Fort  Worth  Limestone. 

3.  Soft  chalky  limestone;  Pecten  bellula,  Pleuroto- 


maria  austinensis 6 

2.  Marl.  Pecten  bellula < 6 

1.  Soft  fragmental  limestone.  Pecten  bellula 6 


Duck  Creek  Marl: 

24.  Soft  marl  with  chalky  limestone  fragments. 
Kingena  (Upper)  horizon  in  lower  half.  Pecten 


wrightii  zone  3 6 

23.  Soft  chalky  limestone.  Kingena  (Upper)  horizon. 

P.  bellula.  Forms  a slight  terrace.  . . 4 

22.  Marl.  Upper  gastropod  horizon.  Turritella,  Ceri- 

thium,  Fusus,  Gyrodes  (?) 2 8 

21.  Soft  sandy  limestone  flag.  Diplopodia  zone 3 

20.  Marl.  Pecten  bellula 3 9 

19.  Soft  chalky  limestone.  Lower  (Main)  Kingena 

zone 1 

18.  Straw  colored  marl 5 

16-17.  Laminated  limestone,  gray  and  iron-stained. 


indurated  locally,  rather  unfossiliferous,  making 
‘horseshoe’  bends  where  the  streams  cut  through 
It,  and  everywhere  forming  the  cap  of  the  Duck 
Creek  escarpment  or  at  least  a break  in  the  topo- 
graphy   4 

(The  section  is  continued  in  the  cut  of  the 
military  road  through  the  Duck  Creek  escarp- 
ment, y±  mile  north  of  the  University). 

16-17.  Laminated  gray  indurated  limestone,  capping 
the  crest  of  the  escarpment.  Kingena  may 


usually  be  found  just  above  it 4 

13-15.  Marl.  Gryphea  corrugata,  Hemiaster  elegans, 

Schloenbachia  sp.  I,  Goniophorus  sp 3 

12.  Crumbling,  marly  limestone.  Pinna  sp.  1 2 

11.  Limy  straw-yellow  marl.  Limonite  fossil  horizon 
(Lower  gastropod  horizon):  Nerinea  sp.  near 

pellucida  Cragin,  Lunatia,  Cinulia,  Cerithium, 
Turbo 1 


The  Geology  of  Tarrant  County 


43 


Thickness 
Feet  Inches 

9-10.  Crumbling  chalky  very  marly  limestone  Crania 


sp.  1.  Hamites  spp 2 

7.8.  Straw  colored  marl 2 

6.  Chalky  or  bluish  impure  limestone 2 


Limestones  and  marls  continue  downward  to  the 
Hamites  zone  in  the  bed  of  the  run. 

SECTION  OF  THE  DUCK  CREEK  FORMATION  IN  THE  RUN 
FROM  SOUTHEAST  CORNER  OF  FOREST  PARK  TO  THE 
FRISCO  SHOPS.  LOCALITY,  3 MILES  SOUTHWEST  OF 
FORT  WORTH  AND  V2  MILE  NORTH  EAST  OF  TEXAS 
CHRISTIAN  UNIVERSITY.  Altitude  of  lower  Kingena 
Zone  at  second  turn  of  car  track,  640  feet. 

Thickness 
Feet  Inches 


Scaphites  member  (Limy  Marl)  : 

17.  Gray  indurated  Limestone 2 

16.  Calcareous  marl 2 

13-15.  Two  equal  limy  ledges  with  thin  interbedded 

marl  layers . 3 

12.  Calcareous  marl  2 

7-11.  Three  thin  limstone  ledges  and  two  thicker  marl 

layers . 5 

6.  Compacted,  closely  bedded,  impure  limestone....  4 


Schloenbachia  sp.  (trinodosa?)  Member.  (Marly  Lime) : 


5.  Compact  limestone 1 0 

Calcareous  marl 6 

4.  Compact  limestone  in  four  equal  layers  with  inter- 
bedded thin  marl.  4 

3.  Compactly  bedded,  lumpy,  in  part  “fucoidal”  lime- 
stone mixed  with  bluish  marl 7 


Desmoceras  member  (Limestone) : 

2.  Bluish  very  impure  limestone,  slightly  marly  at  top, 
but  becoming  more  compact  toward  base  and 


usually  weathering  into  smooth  cliff  faces 12 

1.  Harder  limestone  with  iron  nodular  inclusions. 
Hamites  zone.  2 


(The  members  1-2  are  well  exposed  along  the 
drive-way  in  the  park  near  the  east  entrance). 


44 


University  of  Texas  Bulletin 


Paleontology : Of  the  fossil  zones  to  be  mentioned,  the  Diplo* 
podia  zone  (21), -the  Turrilites"  zone  (19),  the  Crania  zone  (10), 
the  Hamites  spp.  zone  (11)  and  the  Pinna  zone  (6)  will  be  less 
easily  located  by  the  fossils  than  the  others;  however,  they  are 
easily  located  by  their  levels.  The  other  zones,  are  conspicuous. 
The  most  dependable  fossil,  both  in  the  field  and  in  well  borings, 
for  locating  the  Duck  Creek  Marl  is  the  Lower  Kingena  (19). 
The  marl  above  this  Kingena  zone  contains  frequent  P eaten  bel- 
lulaf  which  in  the  Fort  Worth  limestone  is  sparse.  The  portion  of 
the  marl  below  the  Kingena  zone  is  harder  to  diagnose;  it  con- 
tains considerable  numbers  of  Gryphea  corrugaia  and  other  un- 
distinctive  fossils..  The  most  conspicuous  associations  or  synd- 
romes of  fossil  are  the  upper  and  lower  gastropod  horizons,  each 
containing  several  genera.  It  may  be  mentioned  that  iron  pseudo- 
morphs  range  considerably  in  the  Duck  Creek  marl.  The  fauna 
of  the  Duck  Creek,  marl  is  essentially  a shallow  water  fauna  and 
has  been  stated  to  represent  a shallowing  and  oscillating  ocean 
bottom.  The  frequent  turning  of  some  shells,  as  Gryphea  wash- 
itaensis,  convex  side  upward  is  stated  to  indicate  a bottom  dis- 
turbed by  local  currents,  and  there  are  evidences  that  some  other 
shells  were  washed  into  their  place  of  deposition. 

FOSSIL  ZONES  AND  HORIZONS 

Upper  Kingena  Zone : This  zone  containing  many  small 

rounded  brachiopods  at  present  referred  to  the  genus  Kingena 
lies  in  stratum  23  and  the  lower  half  of  24,  about  7 feet  above 
the  main  Kingena  zone.  It  is  thicker  than  the  main  Kingena 
zone,  and  the  Kingenas,  are  much  sparser  than  in  the  main  zone. 
Between  the  two  zones  no  Kingenas  have  been  found  in  situ, 
though  washed  down  individuals  are  abundant  to  below  the 
indurated  ledge  17. 

Upper  Gastropod  Zone:  This  zone,  which  contains  among 

other  genera  Cerithium,  Turrit ella,  Gyrodes  (?),  and  Pleuroto- 
maria  austinensis,  occurs  in  stratum  22,  where  the  gastropods 
are  abundant,  and  in  23-24  where  they  are  sparse.  This  zone 
is  apparently  the  lowest  range  of  Pleurotoniaria  austinensis 
Shumard,  of  which  smooth  individuals  showing  only  the  fii*st 
four  or  five  whorls  are  found.  It  is  a zone  of  abundance  of 


The  Geology  of  Tarrant  County 


45 


Turritella  sp.,  which  is  also  abundant  in  the  lower  Kingena  zone. 
The  Gyrodes  (?)  sp.  has  not  yet  been  found  elsewhere  by  us. 

Diplopodia  Zone:  There  is  a zone  of  abundance  of  Diplopodia 
in  the  arenaceous  limy  flag  ]aver  21.  These  slabs  also  contain 
plates  and  fragments  of  Hemiaster  and  other  echinoids,  Pecten 
subdlpina  and  Lima. 

Lower  (Main)  Kingena  Zone:  This  abundant  brachiopod 

zone,  occupying  stratum  19,  is  about  a foot  thick.  The  material 
above  and  below  it  does  not  contain  brachiopods.  This  is  a soft 
chunky,  limestone  layer  which  weathers  into  scattered  irregular 
angular  fragments  with  intervening  projecting  harder  masses. 
A square  meter  of  area  at  one  locality  contained  260  brachiopods 
of  various  sizes  and  shapes  and  of  probably  several  species.  This 
is  one  of  the  most  persistent,  easily  located,  and  important  hori- 
zons in  the  series  and  has  been  traced  for  miles  in  both  directions 
from  Fort  Worth.  Kingenas  occur  at  the  following  levels,  so  far 
as  known  to  us : 

(1)  Mainstreet  limestone,  an  extensive  horizon  near  middle.  Some 
of  the  individuals  are  much  larger  than  any  found  at  lower 
levels  and  are  intermingled  with  those  of  smaller  size  and  of 
various  shapes,  probably  referable  to  several  species.  This  is 
the  horizon  most  frequently  mentioned  in  the  literature. 

(2)  Denton  marl,  top:  on  the  Noland’s  River  near  Blum.  These 
individuals  were  mostly  of  large  size. 

(3)  Duck  Creek  marl:  Upper  Kingena  zone.  Tarrant  County. 

(4)  Duck  Creek  marl:  Lower  (Main)  Kingena  zone,  Tarrant  County. 

(5)  Duck  Creek  Limestone,  base.  In  Grayson  County  these 
brachiopods  of  the  smaller  size  occur  within  10  feet  of  the 
top  of  the  Kiamitia  conglomerate  in  association  with  Exogyra 
plexa  Cragin,  Schloenbachia  belknapi  Marcou  and  in  Tarrant 
County  they  were  found  at  this  level  in  association  with 
Salenia  sp.,  Plicatula  sp.  and  fish  teeth. 

Turrilites  sp. 

A single  individual  of  a vertically  ribbed  species  was  found  in  the 
lower  Kingena  zone  (19).  This  is  the  only  turrilite  known 
to  us  below  the  base  of  the  Pawpaw  in  the  North  Texas  sec- 
tion. In  the  European  and  Mexican  sections  Turrilites  is  well 
represented  in  the  Vraconien. 


46  University  of  Texas  Bulletin 

Goniophorus  sp. 

This  level  is  characterized  by  a very  restricted  zone  of  a few  inches 
thickness,  containing  great  numbers  of  a minute  salenid,  % 
inch  in  diameter,  which  lias  a star-shaped  apical  system  and 
narrow  linear  sutures. 

Crania  sp. 

A zone  of  Crania  sp.  1 is  contained  in  stratum  10;  the  species  ia  % 
distinctive  but  rare,  having  yet  been  found  nowhere  else  in 
the  series. 

Hamites  spp. 

Several  small  species  of  Hamites  and  related  genera,  quite  dis- 
tinct from  the  species  of  large  Hamites  in  the  basal  Duck 
Creek  limestone,  have  not  been  found  so  far  outside  stratum 
10.  These  individuals  are  rather  rare. 

Pinna  sp.  1. 

A zone  of  Pinna  sp.  with  fine  concentric  and  spined  imbrications 
occurs  in  stratum  6.  It  is  rare  and  distinctive,  but  ranges 
somewhat. 

Lower  Gastropod  Horizon. 

This  is  an  aggregation  of  peculiar  small  iron  stained  mud  casts  and 
iron  pseudomorphs,  occurring  in  strata  9-11.  It  includes 
Lunatia,  Cinulia,  Cerithium,  Turbo,  Nerinea  sp.  near  pellucida 
Cragin,  Schloenbachia  sp.,  Hamites  sp.,  and  S^caphites  sp. 
(top).  Most  of  these  fossils  are  less  than  1 cm.  in  diameter. 
They  are  fairly  abundant.  This  limonite  fauna  occurs  at  the 
Red  River. 

Scaphites  sp.  B. 

This  small  gerontic  ammonite  of  which  usually  only  the  coiled  end  is 
preserved,  practically  characterizes  the  Duck  Creek  Limy 
Marl  member.  In  its  upper  range  it  is  associated  with  the 
iron  stained  fossils  of  the  lower  Gastropod  horizon.  (Strata 
9-11). 


The  Geology  of  Tarrant  County 


47 


The  following  additional  species,  which  range  into  the  Fort 
Worth  limestone,  will  also  be  mentioned  here: 

Pecten  bellula  Cragin 

This  fine  ribbed  pecten  begins  near  the  main  Kingena  zone  (19) 
and  is  frequent  up  to  the  base  of  the  Fort  Worth  limestone 
and  present  to  the  top  stratum  (33)  of  this  formation. 

Pleurotomaria  austinensis  Shumard 

This  gastropod  has  not  been  found  by  us  below  the  Lower  Kin- 
gena zone  (19)  of  the  Duck  Creek  Marl;  it  ranges  into  the 
base  of  the  Fort  Worth  limestone  where  a fine  individual 
with  the  body  volution  and  the  ornamentation  was  found. 
The  last  two  volutions  and  the  markings  are  usually  absent. 

Hemiaster  elegans  Shumard 

This  echinoid  ranges  from  stratum  12  of  the  Duck  Creek  marl  to 
high  in  the  Fort  Worth  limestone,  where  it  has  a zone  of 
abundance  in  the  upper  part  of  the  formation. 

Holaster  simplex  Shumard — low  individuals 

The  low  flat  bottomed  Holasters  range  from  the  indurated  ledge 
(17)  of  the  Duck  Creek  Marly  Lime  to  the  base  of  the  Fort 
Worth  limestone  and  are  abundant  between  the  two  Kingena 
layers.  They  are  mud  casts,  rarely  with  a calcareous  test,  are 
usually  iron  stained  and  faintly  tuberculated. 

Holaster  simplex  Shumard — tall  individuals 

These  tall  and  top  heavy  Holasters  range  from  stratum  20  of 
the  Duck  Creek  marl  to  near  the  top  of  the  Fort  Worth  lime- 
stone, being  more  abundant  in  a zone  near  the  top  of  their 
range. 

Pecten  wrighti  Shumard 

This  strongly  ribbed  pecten  begins  at  stratum  22  of  the  Duck  Creek 
marl  and  is  abundant  in  23-24.  Thereafter  it  is  sparse  and 
disappears  high  in  the  Fort  Worth  limestone.  More  than  one 
species  may  be  involved  in  this  range.  A similar  Pecten  occurs 
in  the  basal  Mainstreet  limestone. 

Schloenbachia  sp.  I. 

This  ammonite  begins  at  the  lower  Kingena  zone  and  ranges  into 
the  base  of  the  Fort  Worth  limestone. 


48 


University  of  Texas  Bulletin 


Gryphea  corrugata  Say. 

This  Kiamitia  and  Duck  Creek  Gryphea  is  conspicuous  in  all  the 
Washita  strata  below  the  indurated  ledge  (17)  of  the  Duck 
Creek  Limy  Marl,  and  is  probably  absent  above  that  point. 

DUCK  CREEK  MARLY  LIME  AND  LIMESTONE 

Brief  Diagnosis:  The  basal  part  of  the  Duck  Creek  formation 
is  a series  of  compact  soft  impure  limestone  strata, 
thicker  bedded  than  the  Fort  Worth  limestone  and  with  less 
interbedding.  It  produces  in  Tarrant  county  the  steep  escarp- 
ment at  the  west  edge  of  the  Fort  Worth  uplands,  but  almost 
never  itself  forms  uplands.  The  series  is  bounded  above  by  the 
Duck  Creek  Limy  Marl  and  below  by  the  Kiamitia  marl,  and  in 
Tarrant  County  is  27  feet  thick.  This  portion  of  the  Duck 
Creek  formation  is  characterized  by  a remarkable  sequence  of 
ammonite  zones  which  locate  with  exactness  the  various  levels 
in  the  formation.  The  sequence  is  divisible  into  four  groups, 
in  part  overlapping:  1.  above,  Bchloenbachia  spp.  of  the  rostrata 
type;  2.  Schlo enbachia  spp.  of  the  inftata  type;  3.  Desmoceras 
horizon ; 4.  Hamites  spp.  horizon,  at  the  base  of  the  formation. 

Fossils  collected  by  Shumard  in  the  Duck  Creek  limestone  of 
Grayson  county,  near  Preston  on  the  Red  River,  were  described 
in  1858  by  Marcou,  who  referred  the  beds  to  the  Gault.  The 
formation  was  first  named  by  Hill,  who  described  its  lithologic 
peculiarities,  mentioned  some  of  its  striking  fossils,  and  defined 
it  so  as  to  include  the  marly  strata  lying  between  the  limestone 
proper  and  the  overlying  Fort  Worth  limestone.  The  Fort 
Worth  limestone  in  the  old  sense  as  used  by  Taff  and  others 
included  the  whole  Duck  Creek  formation  and  at  times  various 
other  formations. 

Descriptions  of  Localities : Good  localities  will  often  be 

found  in  stream  beds  cutting  down  through  the  Duck  Creek  es- 
carpment at  the  west  edge  of  the  Fort  Worth  uplands.  The  nar- 
row strip  occupied  by  this  member  is  usually  rocky,  grassy  and 
marked  at  the  top  by  isolated  clumps  of  shrubs  and  trees. 

TJerraee  topography  is  often  present;  and  in  case  the  Fort 
Worth  limestone  scarp  is  recognized  the  underlying  terrace  is  the 
Duck  Creek  (Kingena)  marl;  the  next  underlying  scarp  is  that 


The  Geology  of  Tarrant  County 


49 


of  the  Duck  Creek  with  the  limestone  at  its  base ; and  the  terrace 
beneath  is  the  Kiamitia  clay  which  makes  usually  a gentle  slope 
downward  to  the  Goodland  limestone  outcrop. 

The  Duck  Creek  limestone  is  prevailingly  an  escarpment 
forming  rock ; very  rarely  is  a Duck  Creek  upland  present,  and 
then  it  is  of  limited  area  and  forms  a transitional  slope  to  the 
underlying  Goodland  escarpment.  Such  an  upland  is  seen  on 
the  Azle  road  northeast  of  the  upper  lake.  More  often  the 
limestone  forms  a divide,  but  in  this  case  it  is  usually  capped 
by  the  harder  Fort  Worth  limestone,  as  on  the  Arlington 
Heights  divide.  Sections  of  the  Duck  Creek  escarpment  are 
well  exposed  in  Forest  Park. 

Several  good  localities  lie  near  the  Azle  road  about  two  miles 
northeast  of  the  upper  lake.  Northeast  of  Moslah  Temple  on 
this  road  eight  and  one-half  miles  northwest  of  Fort  Worth  is 
an  extensive  exposure  of  the  ammonite  zones  of  the  lower  Duck 
Greek.  This  portion  also  forms  the  rim  of  an  amphitheater- 
like depression  on  the  headwaters  of  Marine  Creek,  Azle  road, 
nine  miles  northwest  of  Fort  Worth.  Three  and  a half  miles 
southwest  of  the  court-house  the  formation  is  well  exposed  in 
Forest  Park,  where  complete  sections  may  be  seen  along  a line 
from  the  park  entrance  to  the  Frisco  shops;  stream  cuts  a half 
mile  west  of  the  University  also  afford  good  exposures  of  the 
basal  Duck  Creek.  The  uplands  around  Plover  and  Primrose 
are  well  exposed.  Those  southwest  of  Benbrook  are  poor.  The 
Duck  Creek  limestone  interbedded  with  marl  forms  steep  rocky 
slopes  of  hard  terraced  material  which  for  a few  miles  southwest 
of  Fort  Worth  makes  a conspicuous  escarpment  bordering  the 
broad  alluvial  river  bottom;  this  escarpment  with  the  Fort 
Worth  prairies  above  is  seen  with  striking  effect  from  Benbrook. 


4— Tarrant 


50 


University  of  Texas  Bulletin 


SECTION  OP  DUCK  CREEK  LIMESTONE  IN  FOREST  PARK 
NEAR  EAST  ENTRANCE,  EAST  SIDE  OF  DRIVEWAY. 

(Cemented  Upland  Gravel  and  cross-bedded  sand  at  top  of  section.) 

Thickness 
Feet  Inches 


3.  White  limestone  mixed  with  marl,  containing 
Schloenbachia  sp.  H.,  Pecten  subalpina,  Lima, 

Plioatula,  etc 4 

2.  White  limestone  and  interbedded  marl,  containing 
Desmoceras  sp.  and  Schloenbachia  spp.  aff.  S. 
inflata.  The  Desmoceras  is  more  abundant  in  the 
basal  strata  (B)  12 


1.  Harder  massive  grayish  limestone,  containing  Ham- 

ites  spp.,  Plicatula  sp.,  and  Pecten  subalpina.  . . 2 
This  stratum  is  seen  along  the  driveway  south  of 
the  other  locality. 

The  Kiamitia  formation  is  not  clearly  exposed  at  this  locality. 

A similar  section  is  to  be  seen  in  the  first  run  west  of  the 
University,  while  in  the  run  from  the  Frisco  shops  the  whole 
Duck  Creek  formation  above  the  middle  of  the  Democeras  hori- 
zon, and  most  of  the  Fort  Worth  limestone  are  exposed. 

Paleontology : The  Duck  Creek  ammonite  series  is  one  of  the 
paleontological  landmarks  of  the  Washita  division.  The  Duck 
Creek  limestone  is  nearly  constant  in  thickness  at  least  from 
Woodville,  Oklahoma,  to  Georgetown,  Texas,  and  probably 
farther.  The  contained  ammonite  sequence  is  very  widely  dis- 
tributed, possibly  world-wide. 

A portion  of  this  zonal  sequence  follows,  beginning  at  top : 

Schloenbachia  sp.  H.,  aff.  trinodosa 

Boese. 

Schloenbachia  spp.  F-G,  inflata  group. 

Desmoceras  sp.  B. 

Desmoceras  sp.  A. 

Schloenbachia  sp.  E.  aff.  elobiense  Szajnocha 

Schloenbachia  belknapi  Marcou. 

Inoceramus  comancheanus  Cragin,  I. 

munsoni  Cragin. 

Hamites  spp.  and  other  gerontic  am- 
monites. 


The  Geology  of  Tarrant  County 


51 


FOSSILS  OF  THE  DUCK  CREEK  FORMATION. 


Ostrea  subovata  ( ?)  Shumard. 
Ostrea  sp. 

Gryphea  corrugata  Say. 

Gryphea  washotaensis  Hill 
Pecten  texanus  Roemer. 

Pecten  subalpina  Boese. 

Pecten  bellua  Gragin 
Pecten  wrightii  Shumard 
Pecten  sp. 

Pinna  sp. 

Lima  wacoensis  Roemer 
Inoceramus  comancheanus  Cragin 
Inoceramus  munsoni  Cragin 
Trigonia  sp. 

Pholadomya  sp. 

Gyrodes  sp.  (?) 

Turritella  sp. 

Pleurotomaria  austinensis  Shumard. 
Fusus  sp. 

Cerithium  sp. 

Crania  sp. 


Nerinea  sp. 

Turbo  sp. 

Lunatia  sp. 

Schloenbachia  spp. 

Schloenbachia  belknapi  Marcou 
Hamites  fremonti  (?)  Marcou. 
Hamites  spp. 

Scaphites  sp. 

Turrilites  sp. 

Desmoceras  spp. 

Kingena  wacoensis  (?)  (Roemer). 
Kingena  spp. 

Diplopodia  sp. 

Hemiaster  white!  Clark 
Hemiaster  sp. 

Holaster  simplex  Shumard. 
Hemiaster  elegans  Shumard 
Salenia  sp. 

Callianassa  sp. 

Fish  teeth. 


FORT  WORTH  FORMATION. 


Brief  Diagnosis : The  Fort  Worth  formation  includes  a series 
of  limestone  and  marl  layers,  each  less  than  one  foot  thick,  al- 
ternating rather  regularly  with  each  other.  The  limestones  are 
chalky  and  dead  white,  or  are  indurated,  bluish  interiorly  and 
stained  superficially  with  yellow  or  brown  iron  smears.  The 
strata  underlie  broad  stretches  of  upland  grazing  and  farming 
country  composed  of  a black  soil,  and  in  stream  beds  weather  into 
small  cliff  faces  with  shelf-like  projecting  limestone  layers.  The 
formation  is  thirty  feet  thick  in  Tarrant  County.  It  contains 
numerous  characteristic  fossils,  such  as  Pecten  bellula,  Holaster 
simplex,  Hemiaster  elegans,  Exogyra  americana,  Schloenbachia 
sp.  J,  and  may  be  identified  by  the  following  sequence  of  fossil 
zones  beginning  at  top : 

Enallaster  sp. 

Ostrea  carinata  Lamarck. 

Exogyra  americana  Marcou. 

Hemiaster  elegans  Shumard. 

Pecten  bellula  Cragin. 

Schloenbachia  spp.  of  inflata  type  size 
of  austinensis  Lasswitz. 

Holaster  simplex  Shumard. 

Schloenbachia  sp.  J. 

Pleurotomaria  austinensis  Shumard. 


A nearly  complete  exposure  of  the  Fort  Worth  limestone  and 
the  overlying  Denton  Marl  is  seen  on  the  west  bank  of  Sycamore 
Creek  about  1%  miles  above  its  mouth.  The  limestone  is  ex- 
posed at  several  isolated  localities,  particularly  the  cliff  along 
the  creek  at  the  southwest  corner  of  Glenwood  Park,  which 
gives  the  following  section: 


52  University  of  Texas  Bulletin 

Feet  Inches 

33.  Miarl,  limy  at  top 3 

32.  Soft  impure  limestone.  Enallaster  sp.  2 3 3 

31.  Chalky  limestone 10 

30.  Marl.  Nerinea  sp 8 

2 9.  Limestone  in  4 equal  layers  with  thin  marl  inter- 
bedding . 2 

28.  Loose  crumbly  limestone.... 1 

27.  Solid,  hard,  yellow  stained  limestone 1 8 

26.  Marl 1 6 

25.  Limestone  in  4 equal  layers  with  slight  marl  in- 
terbedding, but  the  bedding  somewhat  irregular 

near  base 2 6 

24.  Compact  coarse  grained  limestone,  iron  stained  and 

locally  sparingly  flinty 1 3 

23.  Limestone,  concretionary  and  fucoidal  at  top,  fol- 
lowed by  compressed  marl  (2"),  limestone  (3") 

and  compressed  marl  (2"). 1 3 

22.  Coarse  limestone,  fucoidal  at  base 1 

20-21.  Coarse  grained  fucoidal  limestone  with  marl  at 

top 1 5 

19.  Lumpy  fucoid  layer  . . . 2 

19.  Brown  marl.  1 

17-18.  Chalky  limestone  with  very  calcareous  coarsely 

laminated  marl  at  base.  . 1 3 

16.  Chalky  concretionary  limestone  8 

15.  Brownish  marl 8 

14.  Chalky  concretionary  limestone 5 

13.  Brownish  marl 5 

12  Hard,  fine-grained,  compact,  slightly  shelly  lime- 
stone, semi-crystalline  and  iron  stained  at  base.  . 7 

11.  Blackish  marl,  brown  or  weathering.  Lima, 

Holaster,  Schloenbachia  sp.  J 6 

10.  Irregular,  chalky  limestone,  Schloenbachia  sp  J.  . 4 

9.  Closely  laminated  calcareous  marl,  slaty  color, 
speckled;  Holaster  simplex,  Pecten  bellula,  Hem- 

iaster  elegans 5 

8.  Limestone,  slightly  lumpy  or  irregularly  bedded.  . 7 

7.  Laminated  marl 3 

6.  Limestone,  irregularly  bedded 8 

5.  Laminated  marl  . 6 

4.  Limestone,  irregularly  bedded 1 10 


TOTAL....  30  1 

The  basal  layers  are  not  exposed  here.  The  whole  Denton  marl, 
showing  its  usual  character,  thickness  and  fossils,  is  exposed  in 
several  places  between  Belzise  Terrace  and  Sycamore  Creek. 


BT  : -'i 


A B 

Fig.  4.  Columnar  sections  of  the  Fort  Worth  limestone.  A.  On 
Sycamore  Creek,  northwest  corner  of  Glenwood  Park,  Fort 
Worth.  The  Denton  marl  immediately  overlies  stratum  33. 
B.  Eastward  facing  exposure  in  a run  y2  mile  east  of  Texas 
Christian  University  and  y2  mile  south  of  Forest  Park,  Fort 
Worth. 

The  numbers  refer  to  corresponding  strata  described  on 
pp.  52-4.  Vertical  scale,  V8  inch  = 1 foot. 


54 


University  of  Texas  Bulletin 


Description  of  Localities : This  formation  in  the  restricted 

sense  adopted  by  Hill  occupies  a strip  of  variable  width  running 
through  the  middle  of  Tarrant  County  from  north  to  south.  The 
type  localities,  % mile  east  of  the  Texas  & Pacific  Railway  sta- 
tion, Port  Worth,  and  on  the  river  bank  just  north  of  the  Court- 
house are  now  almost  obliterated,  the  former  by  erosion,  the 
latter  by  grading  and  overwash.  There  has  been  some  variation 
in  the  nomenclature  of  this  formation,  but  as  eventually  defined, 
it  ‘ ‘ consists  of  a group  of  impure  white  limestones,  very  slightly 
arenaceous,  regularly  banded  in  persistent  layers  averaging 
nearly  a foot  in  thickness  and  alternating  very  regularly  with 
similar  layers  of  marly  clay.  The  limestones  and  marls  occur 
in  strata  4 or  5 inches  to  2 or  more  feet  in  thickness.  The  marly 
layers  alternate  with  the  hard  limestones  in  bands  ranging  from 
thin  laminae  to  beds  6 inches  or  more  thick.”  “Paleontologi- 
cally the  formation  may  be  defined  as  the  horizon  of  Ammonites 
leonensis  and  E piaster  elegans.”  With  little  variation,  the 
following  sections  may  be  taken  as  typical  for  Tarrant  County : 


SECTION  OF  FORT  WORTH  LIMESTONE,  EASTWARD  FACING 
EXPOSURE  IN  RUN  V2  MILE  EAST  OF  TEXAS  CHRISTIAN 
UNIVERSITY,  3 MILES  SOUTHWEST  OF  FORT  WORTH, 
TEXAS.  Altitude,  top  of  exposure,  685  feet. 


Feet  Inches 


25.  Three  thin  limestone  bands  with  2 interbedded 

marl  layers 2 2 

24.  Laminated  marl,  with  a 3"  limy  hand  in  center.  . 1 6 

22-23.  Limestone  in  4 equal  layers  interbedded  with 

thin  much  compressed  limy  marl 2 

21.  Marl  . 6 

18-20.  Limestone  in  3 laminated  equal  layers  inter- 
bedded with  thin,  much  compressed  limy  marl.  .1  8 

18.  Marl 6 


16-17.  Limestone. 


Laminated  marl  ......  ...  ...  2 

Limestone.  ' " 6 

i5i -mm  8 

14.  Limestone . . .;  . . . . . 6 

13.  Marl  10 

12.  Limestone  ...  8 

8-11.  Blue  marly  Limestone 1 6 

4-  7.  Laminated  marl 3 

3.  Limestone 5 


The  basal  strata  1-2  are  exposed  in  the  bend  of  the  stream  just 
north  of  this  locality. 


The  Geology  of  Tarrant  County 


The  formation  is  thus  composed  of  a series  of  alternating  beds 
of  soft  chalky  limestone  and  calcareous  marl.  It  differs  from 
the  upper  Duck  Creek  beds  in  that  there  is  a regular  alternation 
of  lime  and  marl,  no  bed  in  general  is  more  than  1 foot  thick, 
and  the  limestone  strata  indurate,  especially  in  eastward  facing 
exposures  and  form  projecting  ledges,  the  softer  marl  having 
eroded  away.  The  marl  layers  are  compactly  laminated  and 
very  limy  and  grade  evenly  into  the  limestone,  so  that  the  exact 
limits  are  undefined  even  though  they  appear  definite  due  to  tfie 
weathering  of  the  marl  and  the  shelf -like  projection  of  the  lime- 
stone. In  addition  the  hard  layers  vary  slightly  in  thickness 
even  in  the  same  cliff  face  due  to  their  being  composed  of  un- 
even flaky  accretions  of  calcareous  material  cemented  together 
by  limy  marl. 

The  contact  of  the  Fort  Worth  limestone  and  the  Denton  marl 
is  well  shown  at  a point  y2  mile  south  of  the  Frisco  track  and 
4y2  miles  southwest  of  Fort  Worth. 

Denton  Marl  Feet 

3.  Shell  conglomerate  of  Gryphea  washitaensis,  con- 
taining Ostrea  carinata.  Pecten  subalpina,  etc..  1 
2.  Bluish  clay  with  innumerable  Gryphea  washit- 
aensis adults  and  larvel  stages 16 

1.  Brown  sandy  marl  with  many  sandstone  flags.  ...  8 


25 


Fort  Worth  Formation: 

33.  Straw-colored  calcareous  marl  with  limy  fragments. 

Enallaster  sp.  E.  texanus,  Nautilus  texanus, 

Pecten  subalpina,  Schloenbachia  sp.  I,  Holaster 
simplex,  Hemiaster  elegans,  Lima  sp. ..........  3 

32.  Three  limy  strata  with  interbedded  thin  mart  layers  2 

Ihe  lower  Fort  Worth  strata  are  excellently  exposed  along  this 
run. 


Essentially  the  same  sequence  is  seen  north  of  the  Frisco  track,  3 
miles  north  of  Denison  and  along  the  Red  River  in  Cooke 
• County  and  elsewhere. 

' ; • i-xr'  V/:  .'■>  UIJ*  inmtl 

Ihe  base  of  the  Fort  Worth  limestone  is  well  exposed  at  the 
following  locality: 


56 


University  of  Texas  Bulletin 


FORT  WORTH  AND  DUCK  CREEK  FORMATIONS  AT  FIRST 
TURN  OF  CAR  TRACK  % MILE  NORTH  OF  THE  UNIVER- 
SITY AND  3 y2  MILES  SOUTHWEST  OF  FORT  WORTH,  TEXAS. 
Elevation  at  base  of  Fort  Worth  limestone,  680  feet. 


Fort  Worth  Formation:  Feet  Inches 

3.  Soft  chalky  limestone.  Pecten  bellula  Cragin, 

Pleurotomaria  austinensis  Shumard 6 

2.  Marl.  Pecten  bellula 0 

1.  Limestone.  Pecten  bellula 6 

Duck  Creek  Marl: 


34.  Soft  straw  marl  with  chalky  limestone  fragments. 
Upper  Kingena  zone  in  lower  half;  Pecten 


wrightii 3 6 

23.  Soft  chalky  limestone.  Kingena,  upper  zone. 

Pecten  bellula.  Forms  a slight  terrace . 4 

22.  Marl.  Gasttopod  zone:  Globiconcha  (?),  Tur- 

ritella,  Cerithium,  Fusus,  Pleurotomaria 2 8 

21.  Soft  flaggy  arenaceous  limestone.  Diplopodia  zone. 

Hemiaster  plates 3 

20.  Marl.  Pecten  bellula 3 2 

19.  Soft,  chalky  limestone.  Lower  (Main)  Kingena 

zone.  Turrilites  sp 1 

18.  Marl ■ 5 

16-17.  Laminated  gray  limestone,  ironstained,  locally 
indurated,  rather  unfossiliferous,  making  ‘horse- 
shoe’ bends  in  streams 4 


The  rest  of  the  Duck  Creek  formation  is  exposed  in  the  run 
north  of  this  locality. 

It  is  seen  that  the  upper  contact  of  the  formation  is  unmis- 
takeable,  and  that  the  lower  contact  as  here  placed,  leaves  the 
Fort  Worth  limestone  about  30  feet  thick  in  Tarrant  County. 

Paleontology : The  Fort  Worth  limestone  contains  certain 
diagnostic  fossil  zones,  some  of  which  are,  beginning  at  the  top : 

Zone  of  Enallaster  sp.  In  the  uppermost  stratum  (33)  are  two  or 
three  species  of  Enallaster,  of  which  one,  an  elongated  low 
species  occurring  at  this  level  at  Denison,  Fort  Worth, 
Blum  and  elsewhere  has  not  been  seen  at  any  other  level. 


The  Geology  of  Tarrant  County 


57 


Exogyra  americana  Marcou.  This  large  characteristic  oyster  occurs 
in  a restricted  vertical  zone  (25-27)  where  it  is  abundant  and 
easily  recognized.  It  usually  fails  to  weather  out  cleanly. 
It  occurs  at  this  level  from  the  Red  River  to  the  Brazos; 
Dr.  Boese  has  also  found  it  near  the  top  of  the  Duck  Creek 
limestone  in  Grayson  County. 

Ostrea  carinata  (?)  Lamarck.  Fossils  ordinarily  referred  to  this 
species  are  much  more  widely  distributed  in  the  Texas  Coman- 
chean  than  has  been  suspected.  This  species  is  widely  ranging 
and  one  of  its  zones  of  abundance  is  in  the  top  of  the  Fort 
Worth  limestone  (28-29).  The  following  occurrences  are 
known  to  us: 

(1)  Buda  limestone,  Austin,  Texas  (Whitney). 

(2)  Base  of  Mainstreet  limestone,  Fort  Worth  and  Denton,  Texas,  below 

the  Pachymya  zone. 

(3)  Pawpaw  clay,  Fort  Worth,  Texas,  and  elsewhere. 

(4)  Quarry  limestone,  Gainesville  and  Denton,  Texas,  abundant. 

(5)  Top  of  Weno  limestone,  Fort  Worth,  Texas. 

(6)  Denton  marl,  top.  Conglomerate  of  Gryphea  washitaensis  and  Ostrea 

carinata,  widespread  in  north  Texas  (Hill’s  member  i in  21  Ann. 

Rept.  pt.  7,  U.  S.  G.  S.,  pp.  270-71  and  elsewhere). 

(7)  Fort  Worth  Limestone,  top,  zone  below  Exogyra  americana,  Gaines- 

ville, Fort  Worth  and  Krum,  Texas,  and  elsewhere. 

(8)  Basal  Fort  Worth  Limestone  (1)  Fort  Worth,  Texas. 

The  positive  identification  of  the  individuals  awaits  comparison 

with  European  material.  It  may  be  mentioned  that  two  cross- 

sections  are  prevalent;  a triangular  one  and  a semi-elliptical  one. 

Hemiaster  elegans  Shumard. 

This  echinoid  begins  in  stratum  11  of  the  Duck  Creek  Marl  and 
ranges  upward  to  the  top  of  the  Fort  Worth  Limestone, 
with  a zone  of  abundance  in  strata  22-24.  There  is  con- 
siderable variation  among  individuals  referred  to  this 
species,  some  being  larger,  broader  and  much  flatter  than 
others. 

Schloenbachia  sp.  J. 

This  species  ranges  from  the  base  of  the  Fort  Worth  Limestone  to 
the  top.  It  is  most  abundant  in  a broad  zone  near  the 
base  (1-5). 

Holaster  simplex  Shumard. 

Tall,  top-heavy  individuals  referred  to  this  species  range  from 
the  indurated  ledge  (17)  of  the  Duck  Creek  Limy  Marl  to 
the  top  of  the  Fort  Worth,  being  most  abundant  near  the 
middle  of  the  limestone  (22-24). 


58 


University  of  Texas  Bulletin 


Peeten  wrighti  Shumard. 

This  peculiar  Peeten  ranges  from  the  Lower  Kingena  zone  (19) 
of  the  Duck  Creek  Marl  to  the  middle  of  the  Fort  Worth 
and  is  most  abundant  just  below  the  base  of  the  Fort 
Worth  limestone. 

Peeten  bellula  Cragin. 

This  characteristic  fine-ribbed  Peeten  ranges  from  the  lower  Kin- 
gena zone  (19)  to  the  top  of  the  Fort  Worth,  and  is  most 
abundant  in  the  upper  part  of  the  marl. 


FAUNA  OF  THE  FORT  WORTH  LIMESTONE 


Gryphea  washitaensis  Hill 
Exogyra  americana  Marcou 
Ostrea  subovata?  Shumard 
Ostrea  carinata  ? Lamarck 
Ostrea  sp. 

Plicatula  spp. 

Peeten  subalpina  (Boese) 
Peeten  wrighti  (Shumard) 
Peeten  bellula  (Cragin) 

Pinna  sp. 

Trigonia  sp. 

Pachymya  sp. 

Pteria  sp. 

Remondia  ? robbinsi  (White) 
Tapes  sp. 

Protocardia  texana  (Conrad) 
Lima  wacoensis  Roemer 
Lima  sp. 

Pholadomya  shattucki  Boese 
Turritella  marnochi  White 


Turritella  seriatim-granulosa  ? 
Roemer 

Pleurotomaria  austinensis  Shumard 
Cinulia  sp.  aff.  tarrantensis  Cragin 

Nautilus  texanus  Shumard 
Schloenbachia  spp. 

Enallaster  sp. 

Enallaster  texanus  (Roemer) 
Holaster  simplex  Shumard 
Hemiaster  elegans  Shumard 
Hemiaster  sp.  aff.  whitei  Clark 
Epiaster  aguilerae  Boese 
Ophioglypha  texana  Clark 

Trochosmilia  sp. 

Serpula  sp. 

Lamna  sp. 
fucoid  masses 


DENTON  MARL 

Brief  Diagnosis : The  Denton  marl  is  a very  shelly  blue- 

grayish  marl  formation,  25  feet  thick  in  Tarrant  County,  lying 
between  the  Fort  Worth  limestone  below  and  the  Weno  marl 
above.  It  is  characterized  by  a great  abundance  of  the  oyster- 
lake  shells  of  Gryphea  washitaensis , which  especially  near  the 
top  of  the  marl  make  a conglomerate  containing  - also  shells  of 
Ostrea  carinata. 

Lithology:  The  Denton  shell  marl  is  a shallow  water  deposit 
and.  has  the  texture  and  appearance  of  sediments  deposited  in 
modern  seashore  mud  flats.  If  is  excessively  shelly,  the  shells 
being  mainly,;  adults  and  various  young  stages  of  the  oyster, 
Gryphea  washitaensis  Hill;  * ~ ^ ^ ’ 

The  mass  of  the  material  is  a flaky,  non-arenaceous,  laminated 


The  Geology  of  Tarrant  County 


59 


bluish-gray  calcareous  marl,  having  considerable  plasticity.  The 
basal  part  of  the  formation  is  somewhat  sandier,  flaggy  and  less 
fossiliferous.  The  top  of  the  marl  is  a bedded  conglomerate  of 
the  Gryphea  shells,  which  is  usually  slabby  and  breaks  off  into 
considerable  sheets.  The  top  of  the  formation  is  exposed  % 
mile  southeast  of  Our  Lady  of  Victory  Academy,  Fort  Worth, 
between  the  Missouri,  Kansas  and  Texas  Railway  and  the  Inter, 
national  and  Great  Northern  Railway  tracks;  on  Sycamore 
Creek,  in  the  bluff  below  the  Houston  and  Texas  Central  Rail- 
way bridge  and  at  the  waterfall  just  east  of  the  International 
and  Great  Northern  Railway  track,  both  localities  4 miles  south- 
east of  Fort  Worth;  at  points  1 and  2 miles  southeast  of  Haslet 
and  elsewhere.  The  top  of  the  formation  does  not  make  a con- 
spicuous topographic  break  as  in  Grayson  County,  where  it 
forms  a surface  shelf  at  its  outcrops.  The  base  of  the  formation 
is  exposed  at  a point  % mile  southeast  of  the  Frisco  track  and 
5 miles  southwest  of  Fort  Worth,  and  elsewhere. 

SECTION  OF  DENTON  MARL  AT  BLUFF  100  YARDS  NORTH  OF 
THE  HOUSTON  AND  TEXAS  CENTRAL  RAILWAY  BRIDGE 
ACROSS  SYCAMORE  CREEK,  4 MILES  SOUTHEAST  OF  FORT 
WORTH,  TEXAS. 

Weno:  Feet  Inches 

3.  Limestone  . . . 1 

2.  Marl 1 6 

1.  Limestone • 1 

Denton : 


3.  Unfossiliferous  marl  above,  followed  by  Grypbea 
washitaensis  Shell  Conglomerate,  two  layers 
separated  by  a thin  marly  stratum  and  con- 
taining Ostrea  carinata,  Pecten  subalpina, 

Trigonia,  Plicatula,  etc  5 

2.  Blue  shelly  hiarl  with  inconspicuous,  scattered  con- 
glomerate layers  .....  2 1 6 

1.  Brown,  sandy  marl  with  a few  thin,  sandstone  flags. 

Enallaster,  Pecten,  Plicatula,  Lima.  . . 1.  6 


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University  of  Texas  Bulletin 


Feet  Inches 

Fort  Worth: 

33.  Very  calcareous  marl  with  Enallaster  sp.,  Nautilus 

texanus,  Hemiaster  elegans,  Pecten  subalpina . . 3 

2 2-32.  Alternating  limestone  and  marl  layers 20 

(The  lower  portion  of  the  Denton  and  the  Fort 
Worth  limestone  are  seen  farther  down  Sycamore 
Creek) . 

Paleontology : The  Denton  marl  has  few  restricted  fossils 

and  none  that  are  absolutely  distinctive,  so  far  as  now  known. 
The  fauna  is  marked  by  the  abundance  of  Gryphea  washitaensis 
and  by  the  practical  absence  of  ammonites  and  echinoids. 

(a)  Association  of  Trigonia,  Proto  car  dia,  Tapes.  This  loose 
association  of  pelecvpods  occurs  in  the  lower,  more  arenaceous 
part  of  the  Denton  marl  stratum.  It  is  an  aggregation  which  is 
easily  recognized,  though  no  one  species  is  limited  to  this  forma- 
tion. 

(b)  Association  of  Ostrea  carinata  and  Gryphea  ivashitacn- 
sis.  Succeeding  the  uppermost  strata  containing  Hemiaster 
elegans — the  top  of  the  Fort  Worth  limestone — are  marly  strata 
containing  increasing  numbers  of  Gryphea  washitaensis  and 
scattered  individuals  of  Ostrea  carinata.  In  Tarrant  County 
this  shelly  marl  culminates  (stratum  3)  in  two  thin  slabby  lay- 
ers of  shell  conglomerate  composed  almost  entirely  of  Grypheas 
but  containing  frequent  Ostrea  carinata , and  Pecten  subalpina, 
Plicatula  sp.  and  other  fossils. 

Gryphea  washitaemis  Hill  ranges  from  the  lower  Duck  Creek 
limestone  to  basal  Mainstreet  limestone.  Its  zone  of  great- 
est abundance  is  in  the  upper  10  feet  of  the  Denton  marl.  Below 
this  point,  in  both  the  Denton  and  the  Fort  Worth  formations, 
it  is  scattered  but  frequent;  while  in  the  Weno  and  Pawpaw  it 
becomes  gradually  sparser  and  in  Tarrant  County  has  not  been 
found  above  the  basal  Mainstreet.  Ostrea  carinata  occurs  sparsely 
throughout  the  upper  10  feet  of  the  Denton;  it  is  locally  abun- 
dant in  the  conglomerate  slabs  at  the  top  of  the  Denton,  though 
not  so  abundant  as  at  the  Red  River.  This  is  the  main  zone  of 
this  oyster  always  referred  to  in  the  literature;  the  other  oc- 
currences have  been  noted  elsewhere  (p.  57). 

The  association  of  these  two  species  as  a persistent  shell  con- 


The  Geology  of  Tarrant  County 


61 


glomerate  makes  a sheet  of  rock  that  extends  throughout  North 
Central  Texas  at  this  horizon,  and  is  a paleontological  land- 
mark in  the  Washita  division.  As  stated  it  is  thicker  and  more 
prominent  as  a topographic  factor  at  the  Red  River;  at  Fo*t 
Worth  the  conglomerate  is  only  1 foot  thick  and  rarely  with- 
stands erosion,  although  it  marks  the  soil  along  its  outcrop  with 
scattered,  very  easily  recognizable  shelly  slabs.  On  Noland’s 
River,  near  Blum,  the  Denton  is  much  reduced  and  the  con- 
glomerate has  entirely  lost  its  slabby  character,  being  only  a 
loose,  slightly  calcareous  and  uncemented  shell  marl  containing 
Gryp'hea  washitaensis  and  a few  Ostrea  carinata.  Farther  south 
it  is  supposed  to  form  a portion  of  the  Georgetown  limestone. 

FOSSILS  OF  THE  DENTON  MARL 

Leiocidaris  hemigranosus  (?)  Shum-  Nautilus  texanus  Shumard. 
ard.  Lima  wacoensis  Roemer. 

Ostrea  carinata  (?)  Lamarck.  Protocardia  sp. 

Gryphea  washitaensis  Hill.  Trigonia  sp. 

Ostrea  marcoui  Boese.  Ostrea  quadriplicata  Shumard. 

Pecten  subalpina  Boese.  Plicatula  sp. 

Pecten  texanus  Roemer. 


WENO  FORMATION 

Brief  Diagnosis : The  Weno  formation  consists  of  a series  of 
limestones  and  brown  or  yellow  calcareous  marls  containing 
seams  of  limestone  or  ironstone,  lying  above  the  Gryphea  con- 
glomerate of  the  top  of  the  Denton  marl,  and  below  the  Paw- 
paw clays.  It  is  67  feet  thick  on  Sycamore  Creek  near  Fort 
Worth  and  nearly  twice  as  thick  at  the  Red  River.  In  Tarrant 
County  it  is  reduced  in  thickness  but  it  is  not  in  any  way  ‘ ‘ con- 
solidated” (with  the  adjoining  formations)  as  has  been  claimed. 
It  is  abundantly  fossiliferous.  The  top  limit  on  the  Red  River 
is  the  Quarry  Limestone  group,  but  at  Fort  Worth  this  group 
is  reduced  and  is  recognizable  only  with  difficulty;  the  contact 
in  Tarrant  County  is  placed  at  the  junction  of  the  white  chalky 
Weno  limestone  below  and  brown  sandy  clay  containing  pyrite 
fossils,  are  described  later  (p.  67).  The  Denison  and  Gainesville 
sections  of  the  Weno  are  essentially  similar  to  each  other.  As 
we  go  south  from  the  Red  River  the  Weno  thins,  and  becomes 
more  calcareous  and  somewhat  less  fossiliferous.  The  nacreous 
and  chalky  fossils  seen  at  the  Red  River  and  their  ironstone 
casts  and  molds  become  rarer  in  southern  Cooke  County  and  are 


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University  of  Texas  Bulletin 


absent  in  this  form  at  Fort  Worth.  The  separate  members  of 
the  Weno  also  seem  to  thin  towards  the  south. 

As  noted  for  the  Pawpaw  marls  (p.  68),  the  ironstone  seams 
of  the  Bed  Biver  section  are  replaced  in  Tarrant  County,  espe- 
cially north  of  the  Trinity,  by  great  amounts  of  jasper-like  peb- 
bles. The  Weno  appears  prevailingly  as  a yellow  marl  with 
chalky  limestone  layers. 

Description  of  Localities : On  the  east  bank  of  the  upper  half 
of  Sycamore  Creek,  which  runs  nearly  in  the  strike,  there  is 
exposed  for  several  miles  a continuous  section,  from  the  Gervil- 
liopsis  ledge  at  the  top  of  the  lower  third  of  the  Weno,  upwards 
to  the  base  of  the  Mainstreet  limestone.  In  addition,  the  pit  at 
the  Cobb  Brick  Yards,  an  exposure  on  Sycamore  Creek  % mile 
below  the  brickyards  and  two  exposures  near  the  Houston  & 
Texas  Central  Bailway  bridge  across  the  Sycamore  Creek  show 
the  basal  third  of  the  Weno  and  most  of  the  Denton  marl.  These 
localities  are  rich  in  fossils;  and  the  whole  landscape  reveals 
the  very  intimate  relations  between  the  topography  and  the 
underlying  geological  structure.  The  diagrammatic  terrace 
features  correspond  accurately  to  the  formations  beneath  them, 
and  represent  from  bottom  to  top : (a)  the  top  of  the  lower  half 
of  the  Weno  limestone,  usually  an  inconspicuous  terrace;  (b)  the 
top  of  the  Weno  limestone  producing  the  first  main  terrace;  (c) 
the  second  terrace,  composed  of  the  limestone  cap  over  the  Paw- 
paw clay;  and  (d)  an  erosion  slope,  often  terrace-like,  which  rep- 
resents the  Mainstreet  limestone  capping  the  hill.  In  the  portion 
of  Sycamore  Creek  which  runs  nearly  in  the  strike,  the  Gervil- 
liopsis  ledge  forms  the  bed  of  the  creek.  South  from  Sycamore 
Creek  the  Weno-Pawpaw  strip  narrows  and  follows  the  edge  of 
the  reduced  Mainstreet  upland,  close  to  the  west  border  of  the 
Cross  Timbers,  leaving  the  county  west  of  Burleson.  The  out- 
crops are  here  covered  with  Woodbine  and  Mainstreet  overwash. 
Northwards  from  upper  Sycamore  Creek  the  Weno-Pawpaw 
strip  widens  to  about  3 miles  and  spreads  6ver  the  uplands  along 
the  tributaries  of  Sycamore  Creek.  The  cliffs  of  the  two  forma- 
tions, with  the  Mainstreet  upland  above,  border  the  river  valley 
near  Biver  crest  for  several  miles  east  of  Fort  Worth  just  as  the 
Duck  Creek  and  Goodland  escarpments  do  in  the  western  part 


Fig.  5.  Columnar  section  of  the  'Denton,  Weno  fend  Pawpaw 
formations  on  Sycamore  Creek,  3 miles  southeast  of  Fort  Worth. 
The  numbers  refer  to  corresponding  strata  described  on  pp. 
58-69.  Vertical  scale,  y8  inch  = 1 foot. 


64 


University  of  Texas  Bulletin 


of  the  county.  North  of  the  Trinity  the  strip  widens,  is  gently 
sloping  and,  due  to  overwash,  is  mapable  with  difficulty. 

Lower  Weno:  The  Weno  begins  with  two  layers  of  chalky 

limestone  separated  by  a marl  layer  and  lying  just  above  the 
Denton  shell  marl.  Prom  the  base  of  these  two  layers  to  the 
base  of  a hard  white  limestone  stratum  containing  clumps  and 
scattered  individuals  of  Gervilliopsis  invaginata  (White)  is  a 
layer  of  gray-blue  or  slate-colored,  slightly  laminated,  jointed 
argillaceous  marl,  sometimes  called  a ‘pipe  clay.’  It  is  rather 
fossiliferous  and  contains  two  fossils  which  especially  distinguish 
it:  a species  of  Turritella  and  Pecten  sp.  aff.  georgetownensis 
Kniker,  which  differs  from  that  species  in  having  split  ribs  on 
only  the  right  valve.  This  pipe  clay  is  well  exposed  on  the 
northeast  bank  of  Sycomore  Creek,  150  yards  north  of  the  Hous- 
ton and  Texas  Central  Railway  bridge,  where  the  upper  Denton 
marl  is  also  seen.  The  bluish  Denton  marl  becomes  less  shelly 
near  its  top,  and  is  abruptly  followed  by  the  two  thin  ledges, 
each  about  8 inches  thick  and  lying  1 foot  apart.  The  pipe- 
clay is  capped  by  a thin  ledge  of  fragmented  chalky  limestone, 
locally  slabby  and  indurated.  The  lower  Weno  is  15  feet  thick 
on  Sycamore  Creek. 

Middle  Weno ; The  Gervilliopsis  ledge,  which  is  a persistent 
and  reliable  stratigraphic  marker  in  the  county,'  forms  the  bed  of 
Sycamore  Creek  in  its  middle  portion,  where  it  runs  almost  in 
the  strike,  and  elsewhere  very  consistently  forms  the  resist- 
ent  shelf  of  small,  waterfalls,  such  as  those  at  the  crossing  of  the 
Houston  & Texas  Central  and  the  International  & Great  North- 
ern tracks  and  at  the  crossing  of  the  International  & Great 
Northern  track  over  Sycamore  Creek,  both  about  4 miles  south- 
east of  Fort  Worth.  The  ledge  is  often  indurated  and  fucoidal 
and  is  the  base  of  a group  of  marly  limestones  which  extend 
upwards  for  about  34  feet  to  the  top  of  a chalky  limestone  layer 
which  often  makes  a subsidiary  terrace.  At  the  brickyards  1% 
miles  southeast  of  Gainesville,  the  Gervilliopsis  ledge  is  a blue- 
gray  loosely  compacted  marl  1 foot  thick,  containing  great  num- 
bers of  Gervilliopsis  and  other  fossils  and  lying  39  feet  below 
the  top  of  the  Quarry  limestone  group.  In  the  branch  of  Duck 
Creek  1 mile  north  of  the  Union  Station,  Denison,  the  layer  is 
also  well  developed. 


The  Geology  of  Tarrant  County 


65 


Upper  Weno:  The  upper  18  feet  lies  between  the  subsidiary 
terrace  in  the  Weno  and  the  base  of  the  Pawpaw  marls.  It  con- 
sists of  ichalky  white  limestone  and  its  upper  limit  is  distinct, 
since  the  overlying  brown  marl  washes  away  and  leaves  the  top 
of  the  Weno  limestone  as  a projecting  shelf  or  terrace. 

Paleontology : The  following  is  a brief  summary  of  the  Weno 
fossil  sequence: 

Pawpaw  clay:  Py rite  fossil  zone  (p.  69). 

Weno  limestone  and  marl. 

8.  Nautilus  sp.,  Homomya;  Ostrea  carinata  (abundant).  These 
species  and  others  characterize  the  uppermost  Weno  Lime- 
stone. Certain  of  them  occur  in  the  basal  Mainstreet  lime- 
stone. The  Ostrea  carinata  is  conspicuous  and  abundant; 
its  other  occurrences  have  been  noted  (p.  57). 

6-7.  Nodosaria  texana  Conrad. 

The  Weno  occurrence  of  this  fossil  protozoon  is  in  a narrow 
zone  about  19  feet  below  the  top  of  the  Weno.  Nodosaria 
also  occurs  in  the  base  of  the  Pawpaw  in  North  Texas; 
in  the  Denison  Beds  at  Cerro  de  Muleros;  and  in  the  Del 
Rio  Clays,  in  association  with  Exogyra  arietina  Roemer  in 
South  Texas 

5.  Gervilliopsis  invaginata  (White) 

The  main  zone  of  occurrence  of  this  fossil  is  at  the  top 
of  the  ‘pipeclay’.  Its  other  occurences  have  been  noted. 

1-4.  Turritella  sp.,  Pecten  sp.  near  georgetownensis,  Remondia 
acuminata  Cragin. 

These  species  are  frequent  in  the  basal  part  of  the  Wenu 
pipeclay,  where  there  exists  a considerable  fossil  sequence 
that  will  not  be  discussed  here. 

Denton  marl:  Gryphea  washithensis  (abundant)  and  Ostrea  car- 

inata. 


&— Tarrant 


66 


University  of  Texas  Bulletin 


FOSSILS  OF  THE  WENO  FORMATION  IN  TARRANT  COUNTY  (PAR- 
TIAL LIST) 


Trochosmilia  sp. 
Hemiaster  calvini 
Hemiaster  sp. 

Enallaster  bravoensis 
Enallaster  texanus  ? 
Holaster  sp. 

Cottaldia  sp. 

Leiocidaris  hemigranosa 
Nodosaria  texana 
Pentagonaster  sp. 
Trochosmilia  sp. 
Turritella  sp 
Cinulia  sp. 

Anchura  sp. 

Turbo  sp. 

Trochus  sp. 
Schloenbachia  sp. 

Schl.  sp.  like  inflata 
Hamites  sp. 

Engonoceras  sp. 

Nautilus  texanus 
Homomya  sp. 

Pecten  subalpina 
Pecten  texanus 
Plicatula  sp. 

Corbula  sp. 

Tapes  sp. 

Nucula  sp. 

Astarte  acuminata 
Protocardia  sp. 

Ostrea  quadriplicata 
Ostrea  carinata 
Gryphea  washitaensis 
Trigonia  sp. 

Gervilliopsis  invaginata 
Ostrea  sp.  near  marcoui 
Lima  sp. 

Lamna  sp. 

Oxyrhina  sp. 


Weno  Pawpaw  Mainstreet  Grayson  Buda 

5(!  ' $ 

* * * * * 

* * 

* * 

* * 

5$C  *}« 

* 

* * * 

* * 

* 

* * 

* 


The  Geology  of  Tarrant  County 


67 


PAWPAW  FORMATION 

Brief  Diagnosis : This  formation  on  Sycamore  Creek  consists 
of  23  feet  of  brown  arenaceous  clay,  lying  below  the  hard, 
white  Mainstreet  limestone,  and  above  the  softer  chalky  lime- 
stone which  forms  the  cap  of  the  Weno  formation.  This  brown 
clay  contains  sandy  slabs  in  its  basal  half  and  carries  a charac- 
teristic assortment  of  fossils.  On  account  of  its  totally  different 
color,  hardness  and  composition,  it  should  be  easily  recognized 
and  separated  from  the  adjoining  formation  in  well  drilling. 
Due  to  its  increment  in  thickness  northwards  it  is  about  27' 
thick  at  the  Denton-Tarrant  County  Line,  while  at  the  Tar- 
rant-Johnson  County  line  it  is  about  12  feet  thick.  The  pre- 
vailing texture  is  sandy,  the  soil  is  acidic,  the  vegetation  sparse; 
the  slopes  are  variable,  sometimes  gentle  but  usually  steep,  mak- 
ing a narrow  outcrop  and  good  exposures.  There  is  a sudden 
and  marked  increase  in  the  amount  of  ironstone  fragments  in 
the  Pawpaw  northwards  from  the  Trinity.  The  prevailing  as- 
pect of  the  formation,  aside  from  this  red  material,  is  brown 
sandy-flaggy.  The  Pawpaw  contains  characteristic  and  unmis- 
takable fossils.  At  the  Pawpaw  pit  of  the  Cobb  brickyards,  Fort 
Worth,  the  total  section  is  exposed,  and  shows  a resistant,  firm 
ironstained  brown  clay  with  ironstone,  bituminous  arenaceous 
and  limy  seams. 

Description  of  Localities : There  are  numerous  localities  in 

Tarrant  County,  lying  above  the  terrace  formed  by  the  top  of 
the  Weno  limestone  and  weathering  into  a steep  barren  slope 
filled  with  sandy  flags  and  limestone  fragments.  Such  slopes  in 
stream  cuttings  often  recede  considerably  from  the  face  of  the 
Weno  terrace  and  form  extensive  amphitheatre-like  basins 
whose  sides  are  continuous  exposures  of  the  whole  Pawpaw  and 
whose  floors  along  the  streamlets  contain  fine  concentrations  of 
the  small  fossils  which  occur  near  the  base  of  the  clay.  Such  lo- 
calities occur  along  the  middle  and  upper  portions  of  Sycamore 
creek  especially  near  the  International  and  Great  Northern  rail- 
way bridge  and  thence  northwards  to  the  river;  along  the 
Trinity  valley  southeast  of  Riverside;  at  several  localities 
southeast  of  Haslet;  near  Watauga;  and  near  the  Cleburne  road 


68 


University  of  Texas  Bulletin 


south  of  Fort  Worth.  The  localities  are  just  underneath  the 
western  border  of  the  Mainstreet  limestone  and  naturally  are 
contaminated  with  rock  and  fossils  from  that  formation. 

SECTION  OF  PAWPAW  CLAYS  ON  SYCAMORE  CREEK  NEAR 
THE  HOUSTON  AND  TEXAS  CENTRAL  RAILWAY,  4 MILES 
SOUTHEAST  OF  FORT  WORTH,  TEXAS: 

Feet 

4.  Brown  slabby  argillaceous  thin  limestone  layers 
with  considerable  interbedded  marl  and  scattered 
jasper  pebbles.  Nautilus  sp.  Hemiaster  sp.,  Pec- 

ten  subalpina;  Plicatula  sp 13 

3 Brown  clay  with  scattered  flags.  Turrilites  sp 6 

2.  Sandy  flagstone,  fragile,  containing  Metopaster  sp. 

1.  Brown  clay  with  pyrite  and  other  fossils 3 


23 

SECTION  EAST  OF  KELLER  ROAD,  1 MILE  SOUTH  OF  HASLET, 
TEXAS: 

(Mainstreet  limestone  forms  thin  cap  of  hills 
around  amphitheater.) 

3-4.  Brown  clay  with  flaggy  and  slabby  dimension 
layers  and  great  quantities  of  ironstone  pebbles. 


Few  fossils 22  8 

2.  Flaggy  layer 4 

1.  Brown  clay  with  pyrite  fossils 4 


27 

From  these  sections  the  increment  in  thickness  towards  the 
Red  River  is  visible  within  Tarrant  County. 

PALEONTOLOGY 

3-4.  Nautilus  sp.  and  Hemiaster  sp. 

The  upper  portion  of  the  formation,  especially  the  upper  5 
feet  contains  a small  species  of  Nautilus  and  a rotund  bulky 
species  of  Hemiaster.  The  middle  part  of  the  formation 
contains  Nautilus  sp.  near  texanus,  Pecten  subatpina,  Plica- 
tula, etc. 


Inches 


The  Geology  of  Tarrant  County 


69 


2.  Metopaster  sp. 

A thin  flaggy  stratum  about  4 feet  above  the  base  of  the 
Pawpaw  contains  the  starfish  Metopaster  sp.,  which  so  far 
has  not  been  found  elsewhere  and  may  prove  to  be  narrowly 
limited.  The  zone  also  contains  other  species  of  starfish. 


1.  ‘Pyrite  Fossil  Zone’. 


Approximately  the  lower  8 feet  of  the  clay  contains  an  assort- 
ment of  iron  pseudomorphs  and  other  fossils  which  is  dis- 
tinctive and  includes  the  following: 


Turrilites  sp. 
Schloenbachia  sp. 
Scaphites  sp.  A. 
Hamites  sp. 

Area  sp. 
Engonoceras  sp. 
Cinulia  sp. 


Enallaster  sp. 

Salenia  sp. 

Fish  teeth  and  vertebrae. 
Baculites  sp: 

Flickia  sp. 

Acanthoceras  sp. 
Mortoniceras  spp. 


The  zone  is  present  at  this  level  at  all  localities  in  Tarrant  County. 
The  Turrilites  are  distinctive,  and  none  has  been  found  by  us 
below  the  Pawpaw  except  a solitary  vertically  ribbed  species  in  th« 
Main  Kingena  zone  of  the  Duck  Creek  marl. 

For  brevity  we  call  this  a pyrite  fauna;  some  fossils  are  pyrite, 
some  hematite  and  some  limonite. 


MAINSTREET  FORMATION 

Brief  Diagnosis : The  Mainstreet  limestone,  the  second  most 
important  upland  forming  rock  in  Tarrant  County,  underlies 
a belt  of  irregular  width  just  west  of  the  Eastern  (Woodbine) 
Cross  Timbers.  Its  outcrop  is  a dissected  dip  plain  modified 
by  erosional  slope  towards  the  stream  valleys,  and  is  essen- 
tially similar  to  the  Fort  Worth  limestone  prairie.  The  Gray- 
son marl  lies  between  it  and  the  Woodbine  Cross  Timbers,  and 
the  brown  Pawpaw  clays  underlie  it.  It  is  thus  sharply  limited 
both  above  and  below  and  should  be  recognizable  in  well  drill- 
ing. It  is  characterized  by  the  sequence  of  fossils  listed  later. 
The  Mainstreet  limestone  totals  about  50  feet  in  thickness  at 
Fort  Worth. 

Lithology : The  formation  with  little  variations  from  top  to 

bottom,  is  composed  of  regularly  alternating  strata  of  straw- 
colored  marl  and  chalky,  or  hard  fairly  pure  limestone.  The 
bands  do  not  usually  exceed  one  foot  in  thickness  and  the 


70  University  of  Texas  Bulletin 

formation  has  a deceptive  similarity  to  the  Fort  Worth  lime- 
stone. 

Description  of  Localities:  This  limestone  forms  conspicuous 

and  extensive  uplands.  In  general  appearance  these  are  much 
like  those  formed  by  the  Fort  Worth  limestone.  The  uplands 
of  the  Mainstreet  limestone  extend  from  one  end  of  the  county 
to  the  other  in  a north  south  line  passing  east  of  Fort  Worth. 
The  extensive  and  gently  rolling  area  between  the  Burleson 
and  the  Cleburne  roads  in  the  southern  part  of  the  county  is 
underlain  by  this  formation.  Good  exposures  may  be  seen 
along  Sycamore  creek,  from  the  region  of  the  Glen  Garden 
country  club  southeast:  in  the  stream  cuts  between  Seminary 
hill  and  Crowley;  along  the  road  from  the  Burleson  pike  to 
Crowley,  where  almost  the  entire  thickness  is  passed  through; 
near  Keller,  and  other  parts  of  the  county.  The  lowest  strata 
are  well  exposed  in  Sycamore  Creek  about  one  half  mile  north 
of  Crowley.  This  part  of  the  formation  is  highly  fossiliferous, 
Holectypus  limitis  (?)  and  P achy  my  a sp.  aff.  austinensis  being 
especially  abundant.  Turrilites  brazoensis  which  ranges 
throughout  the  formation  occurs  here,  but  is  more  abundant 
higher  up,  as  in  the  exposures  along  Deer  Creek  between  Burle- 
son and  Crowley. 

The  upper  portions  of  the  formation  are  well  exposed  at 
various  places  along  the  Keller  road,  especially  just  south  of 
Keller. 

The  upper  portion  may  be  seen  also  at  the  crossing  of  the 
Mansfield  road  and  the  Cleburne-Fort  Worth  interurban  rail- 
way. 

Paleontology : The  Mainstreet  limestone  can  be  identified 

and  its  levels  distinguished  by  means  of  the  fossil  sequence, 
which  in  part  is  as  follows : 

Leiocidaris  sp.  Rarely  spines  of  this  echinoid  are  seen  high  in 
the  Mainstreet  formation.  Cyphosoma  and  other  echinoids  are  as- 
sociated with  it.  It  lies  nearly  at  the  top  under  the  level  of 
Exogyra  sp.  2 which  occurs  in  the  basal  chalky  marl  of  the  Grayson 
formation. 

Turrilites  brazoensis  Shumard.  The  upper  ten  feet  or  so  of  the 


The  Geology  of  Tarrant  County 


71 


Mainstreet  formation  is  rather  barren;  below  this,  Turrilites  ap- 
pears and  ranges  downward  as  low  as  the  Holectypus  zone,  which 
is  about  eight  feet  above  the  base  of  the ‘formation.  The  greatest 
abundance  of  Turrilites  is  about  eighteen  feet  below  the  top  of  the 
formation.  It  may  be  seen  in  greatest  abundance  at  the  Deer 
Creek  crossing  of  the  Cleburne  interurban. 

Kingena  wacoensis?  Roemer.  This  distinctive  large  brachiopod 
is  not  found  outside  of  the  Mainstreet  limestone  except  possibly 
in  the  Denton  marl  of  the  southern  section.  A zone  of  great 
abundance  and  almost  the  highest  occurence  is  about  20  feet  above 
the  base  of  the  formation;  the  lower  limit  is  the  base  of  the  forma- 
tion itself. 

Scliloenbachia  sp.  O,  like  inflata.  Throughout  the  Mainstreet. 

Exogyra  arietina  Roemer.  This  tall  spired  Exogyra  begins  about 
the  middle  of  the  Mainstreet  limestone  and  ranges  upward  into  the 
basal  Grayson. 

Ostrea  quadriplicata  Shumard.  This  characteristic  fossil  of  the 
Denton,  Weno  and  Pawpaw  formations  has  not  been  seen  above 
the  basal  Mainstreet,  where  it  is  rare. 

Holectypus  limitis  (?)  Boese.  Large  sized  Holectypus  are  abun- 
dant in  a zone  about  eight  feet  above  the  base  of  the  Mainstreet 
formation. 


Ostrea  carinata  Lamarck.  One  of  the  numerous  but  distinctive 
occurences  of  this  striking  oyster  is  a stratum  in  the  basal  Main- 
street  limestone.  This  and  the  following  zone  may  be  seen  along 
the  Cleburne  road. 

Pachymya  sp.  aff.  austinensis  Shumard,.  A narrow  zone  of  this  fos- 
sil characterizes  the  base  of  the  Mainstreet,  where  numerous  well 
preserved  individuals  occur.  We  have  seen  it  elsewhere  only  in  the 
middle  of  the  Weno  limestone. 


FOSSILS  OF  THE  MAINSTREET  FORMATION  (PARTIAL  LIST) 


Ostrea  sp.,  aff.  marcoui  Boese 
Ostrea  carinata  (?)  Lamarck. 
Ostrea  quadriplicata  Shumard 
Lopha  sp. 

Ostrea  subovata  Shumard. 
Exogyra  arietina  Roemer. 
Exogyra  sp. 

Gryphea  sp. 

Pecten  texanus  Roemer 
Pecten  subalpina  Boese 
Pecten  wrightii  Shumard 
Pecten  roemeri  Hill 
Pecten  spp. 

Spondylus  cragini  Whitney. 

Lima  wacoensis  Roemer. 
Protocardia  vaughani  Shat.tuck. 
Pholadomya  shattucki  Boese. 
Ptychomya  ragsdalei  Cragin 


Pachymya  sp.  aff.  austinensis 
Shumard 
Homomya  sp. 

Barbatia  Simondsi  Whitney 
Trigonia  sp. 

Schloenbachia  sp.  aff.  inflata. 
Turrilites  brazoensis  Shumard. 
Turrilites  sp. 

Nautilus  texanus  Shumard. 
Nautilus  hilli  Shattuck. 

Kingena  wacoensis  (?)  Roemer. 
Cyphosoma  volanum  Cragin. 
Holectypus  limitis  (?)  Boese. 
Enallaster  bravoensis  Boese. 
Enallaster  sp. 

Hemiaster  sp. 

Leiocidaris  sp.  aff.  hemigranosus 

Shumard. 


72 


University  of  Texas  Bulletin 

GRAYSON  MARL 


Brief  Diagnonsis : The  Grayson  marl  in  Tarrant  county  is 

exposed  either  as  a steep  narrow  marl  band  lying  against  the 
western  margin  of  the  Woodbine  Cross  Timbers  or  as  a gentle 
slope  connecting  the  Woodbine  sands  with  the  Mainstreet  up- 
land. In  either  case  it  is  at  nearly  all  places  covered  with  over- 
wash and  vegetation.  Exposures  are  more  rare  than  in  any 
other  Comanchean  formation.  The  marl  is  yellowish-brown  and 
locally  contains  pyrite  seams  and  fossils,  gypsum,  and  inter- 
spersed thin  limestone  bands.  The  formation  is  about  50  feet 
thick  at  its  outcrops  near  Fort  Worth. 

^Descriptions  of  Localities : The  best  and  most  accessible 

localities  are  a cliff  one  mile  east,  and  a small  divide  about  two 
uiiles  southeast  of  Burleson,  just  outside  of  Tarrant  county. 
The  slopes  of  the  Woodbine  hills  just  west  and  northwest  of 
Burleson  also  bear  isolated  exposures  of  the  Grayson  marl.  The 
Texas  and  Pacific  railway  cut.  one-fourth  mile  east  of  Handley 
exposes  the  middle  portion  of  the  formation,  as  do  small  stream 
cuts  one  mile  west  of  Handley. 

SECTION  OP  THE  GRAYSON  MARL,  2 MILES  SOUTHEAST  OF 

BURLESON,  JOHNSON  COUNTY. 

Feet 

3.  Yellowish  calcareous  marl,  sparsely  fossiliferous 12 

2.  Shelly  limestone  band 1 

1.  Yellowish  calcareous  marl,  with  gypsum,  pyrite  and  limonite. 
Gryphea  mucronata,  Exogyra  sp.,  Pecten  subalpina,  Hemi- 
aster  calvini,  Enallaster  sp.,  Turrilites  sp.,  Lima  sp.,  Engon- 

oceras  sp.,  abundant  small  pyrite  fossils *...15 

(Top  and  base  of  Grayson  marl  not  exposed  here). 

No  locality  clearly  showing  the  Grayson- Woodbine  contact 
has  yet  come  to  light  in  Tarrant  county.  This  contact  has  been 
claimed  by  Taff  to  be  unconformable  at  the  locality  on  the  Red 
River  in  Cooke  county,  which  is  now  much  obscured  by  Wood- 
bine overwash.  The  Grayson  marl  locality  just  east  of  Burleson 
is  rich  in  Pecten  subalpina,  Lima  sp.,  Gryphea  mucronata,  and 
•contains  Cyphosoma  volanum,  Hemiaster  calvinif  Enallaster 
bravoensis  and  Engonoceras. 


The  Geology  of  Tarrant  County 


73 


None  of  these  exposures  shows  the  entire  thickness  of  the 
Grayson  marl.  In  the  cliff  east  of  Burleson  about  50  feet  is  ex- 
posed, reaching  not  quite  to  the  Grayson- Woodbine  contact; 
while  between,  the  bottom  of  the  exposure  and  the  Mainstreet 
limestone  near  Village  Creek  there  is  at  least  20  more  feet  of 
basal  Grayson.  Part  of  these  basal  strata  are  seen  at  the 
locality  2 miles  southeast  of  Burleson.  At  Handley  likewise,  the 
Grayson  is  probably  about  70  feet  thick,  and  here  as  usually 
the  upper  part  is  mantled  by  Woodbine  overwash,  a sandy,  red, 
timbered  soil  whose , presence  everywhere  makes  the  Grayson  ap- 
pear abnormally  thin. 

Perhaps  the  completest  exposure  known  is  in  a tall  bluff  3 
miles  ESE.  of  the  bridge  of  the  Fort  Worth-Denton  road  over 
Denton  Creek,  east  of  Roanoke,  Texas.  This  shows  an  appar- 
ently conformable  contact  of  the  Grayson  with  the  overlying 
Woodbine,  and  also  the  contact  with  the  underlying  Mainstreet 
limestone.  The  .Grayson  here  is  75.2  feet  thick. 

GRAYSON  MARL  NEAR  ROANOKE,  TEXAS 

WOODBINE: 

Red  ledge,  forming  crown  of  hill. 

Feet 

GRAYSON: 

Soft  gray  marl  containing  eleven  limestone  ledges,  each  3 to  12 
inches  thick,  the  uppermost  lying  in  contact  and  conformable 
with  the  base  of  the  Woodbine. 

Lima  sp.,  Protocar dia  sp.,  (same  as  the  Weno  sp.),  Cidarid 
spines  (very  large),  zone  of  Hemiaster  calvini  and  Enallaster 
bravoensis  (10  feet  below  top),  Schloenbachia  sp.,  Gyprimeria 
sp.,  Gryphea  mucronata  (scarce),  Pecten  texanus  (abundant), 


PUcatula  (abundant),  Scaphites  ? sp 37.8 

Yellowish  limonite  stained  marl.  Rich  in  Gryphea  mucronata. 
Turrilites  (small  sp.),  no  other  ammonites  seen;  no  echinoids 

seen.  Pecten  texanus,  less  abundant  than  above 15.2 

Soft  gray  marl.  Fossils  scarce,  mostly  Engonoceras  sp.,  Gryphea 
mucronata  and  flattened  Exogyra  arietina.  A number  of  red 
ironstone  seams  weathering  out  black 22.2 


MAINSTREET  LIMESTONE: 

Top:  Kingena  sp.  very  abundant. 

This  locality  is  noticeably  more  calcareous  than  those  farther  west. 


74 


University  of  Texas  Bulletin 


SEQUENCE  OF  GRAYSON  FOSSILS 


The  following  paleontological  sequence  is  taken  from  the  Bur- 
leson, Roanoke  and  Denison  localities : 

WOODBINE:  Ostrea  carica  and  spp.  Seen  at  Burleson  and  else- 

where immediately  overlying  the  Grayson. 

GRAYSON: 

a.  Zone  of  abundance  of  Hemiaster  calvini  and  Enallaster  bravo- 

ensis  about  10  feet  below  top.  Associated  fossils:  Pecten  sub- 

alpina,  Pecten  texanus,  Lima  sp.,  Protocard'ia  sp.,  Cyprimeria  sp. 

b.  Zone  of  Acanthoceras  sp.  and  Tissotia  ? sp.  20-30  feet  below  top. 

Associated  fossils:  Gyphosoma  volanum,  Pachymya  sp.,  Proto- 

car dia  texana,  Turrilites  (small  sp.,  ranges  down  to  Pawpaw). 

c.  Zone  of  abundance  of  Gryphea  mucronata.  Associated  fossils: 

Pecten  texanus,  P.  sp.  aff.  subalpina,  Inoceramus  sp.  45  feet 
below  top  of  Grayson. 

d.  Exogyra  sp.  1.  Associated  with  Pectens,  Gryphea  and  Lima. 

45-55feet  below  top. 

e.  Engonoceras  sp.  About  65  feet  below  top. 

f.  Association  of  Nautilus,  Enallaster  bravoensis,  Enallaster  sp.  near 

texanus,  Holectypus  limitis,  Gryphea  mucronata,  a salenid,  Pec- 
ten, Lima  and  other  pelecypods. 

g.  Exogyra  arietina  and  sp.  This  zone  lies  just  beneath  the  preced- 

ing, at  the  base  of  the  Grayson.  Turrilites  sp.  is  abundant  in 
both  layers.  The  zone  is  underlain  by  Mainstreet  limestone 
containing  abundant  Kingena. 


Brief  Diagnosis : The  Woodbine  formation  is  a series  of 

sandy ; iron  stained,  argillaceous  clay  strata  and  ironstone; 
which  weathers  into  low  rolling  hills  with  open  glades  and  flats 
of  bottom  land.  The  outcrop,  which  covers  roughly  the  eastern 
third  of  Tarrant  county,  is  heavily  timbered  with  black  jack 


FOSSILS  OF  THE  GRAYSON  MARL 


Gryphea  sp.  like  corrugata  Say. 
Gryphea  mucronata  Gabb. 
Exogyra  spp.  1-3. 

Exogyra  arietina  Roemer. 
Exogyra  sp.  like  texana  Roemer. 
Pecten  subalpina  (Boese). 
Turrilites  spp.  1-2. 

Area  sp. 

Lima  sp. 

Gyphosoma  volanum  Cragin. 
Ostrea  sp. 


Anomia  sp. 

Plicatula  spp. 

Protocardia  sp. 

Tapes  sp. 

Pholadomya  shattucki  Boese. 
T'rigonia  sp. 

Cerithium  sp. 

Cinulia  pelletti  Whitney. 
Turritella  sp. 

Hemiaster  calvini  Clark. 
Enallaster  bravoensis  Boese. 


WOODBINE  FORMATION 


The  Geology  of  Tarrant  County  75 

oak  and  post  oak,  and  is  known  as  the  Eastern  (Upper)  Cross 
Timbers. 

The  soil  is  sandy,  red,  and  acidic,  and  is  suitable  for  special 
purposes  as  fruit  growing.  The  outcrop  forms  the  catchment 
area  for  the  Woodbine  artesian  reservoir  whose  water  bearing 
sands  dip  eastward,  underlying  at  an  increasing  depth  a large 
area  in  north  central  Texas. 

The  Woodbine  has  been  divided  into  two  divisions,  the  lower 
(Dexter)  sands  and  the  upper  (Lewisville)  beds.  The  latter 
are  locally  fossiliferous.  The  series  has  been  considered  about 
300  feet  thick  between  Handley  and  Arlington. 

R.  T.  Hill 1 gives  the  following  excellent  description  of  the 
Woodbine  formation:  “The  rocks  of  the  Woodbine  formation 

are  largely  made  up  of  ferruginous,  argillaceous  sands,  char- 
acterized by  intense  brownish  discoloration  in  places,  which  are 
accompanied  by  bituminous  laminated  clays.  These  sands,  like 
those  of  the  Trinity  division,  are  unconsolidated  in  places,  but 
differ  from  them  by  containing  a greater  proportion  of  iron 
and  other  mineral  salts,  which  materially  influence  the  char- 
acter of  the  waters  derived  from  them.  The  sand,  which  in  the 
unoxidized  substructure  are  usually  white  and  friable  contain 
particles  of  iron  occurring  with  glauconite  and  pyrite.  These 
minerals  oxidize  toward  the  superficies,  and  their  solutions  con- 
solidate the  more  porous  beds  of  sand  into  dark  brown  siliceous 
iron  ore,  occuring  in  immense  quantities  in  certain  localities. 
Other  beds  of  sand  break  down  into  deep  loose  soils.  These 
support  a vigorous  timber  growth.’’ 

Description  of  Localities : The  Woodbine  sands  are  poorly 

exposed  in  Tarrant  county  due  to  the  small,  inconsecutive  sec- 
tions, the  softness  of  the  strata  and  the  consequent  very  general 
overwash,  and  the  extensive  timbering.  The  best  series  of  ex- 
posures is  along  the  road  east  of  Birdville,  and  the  Rock  Island 
railway  cuts  east  of  Tarrant  station.  The  basal  contact  of  the 
Woodbine  was  not  anywhere  seen  with  clearness,  altho  localities 
near  Burleson  and  Handley  have  the  basal  part  poorly  exposed. 
The  upper  contact  with  the  Eagle  Ford  shales  is  seen  in  Taff’s 

’Hill,  21st  Ann.  Rept.  U.  S.  (G.  S.,  part  7,  p.  294. 


76 


University  of  Texas  Bulletin 


locality  on  Bear  Creek,  % of  a mile  west  of  the  Tarrant-Dallas 
county  line  and  2 y2  miles  northeast  of  Tarrant.  A few  basal 
strata  are  visible  in  cuts  of  the  Fort  Worth-D alias  interurban, 
2 miles  east  of  Handley. 

An  excellent  section  of  part  of  the  Woodbine  formation  near 
the  base  is  seen  at  the  pit  of  the  Acme  brick  yards,  Denton, 
Texas.  This  section  is  forty-two  feet  deep,  and  is  strongly  acidic 
in  all  of  its  material.  The  alternation  of  argillaceous  bands 
with  pure  sandstone  beds  is  striking.  There  is  a perceptible 
stratification,  apparently  with  conformable  members,  except  at 
the  top.  Here  there  is  either  the  end  of  a lenticular  mass  or 
the  beds  represent  the  foreset  laminae  of  strong  cross  bedding. 
The  former  is  the  more  likely,  especially  since  about  a mile 
distant  and  in  the  plane  of  the  cut,  a similar  group  of  beds  is 
shown  whose  dip  is  strongly  against  that  of  the  beds,  suggesting 
the  other  edge  of  the  lenticular  mass. 

SECTION  IN  THE  PIT  OF  THE  ACME  BRICK  YARDS,  DENTON, 
TEXAS: 

Feet 

5.  Lenticular  mass,  four  members,  overlain  by  a red  sandy 


clay 15 

4.  Light  colored  limonitic  argillaceous  member 7 

3.  Red  sandstone  5 

2.  Light  colored  limonitic  argillaceous  member 1 

1.  Grayish  sandy  argillaceous  member,  containing  several 

bands  of  almost  black  sandstone 14 


42 

A 25  foot  boring  at  this  point  penetrated  the  Grayson  marl. 

/ SECTION  OF  WOODBINE  EAST  OF  TARRANT  STATION 

(The  following  section  is  seen  south  of  the  railroad  below  the 
first  bridge  west  of  the  county  line.) 

Feet  Inches 

27.  Sandstone  ledge,  locally  a shell  conglomerate,  con- 
taining Barbatia  micronema  Meek,  Ostrea 
soleniscus  Meek,  Ostrea  carica  Cragin,  Ostrea  sp., 

Exogyra  sp.,  and  other  Lewisville  fossils.  The 
upper  portion  is  indurated,  laminated  and  espe- 
cially fossiliferous.  Exposed  in  three  cuts  nearest 


The  Geology  of  Tarrant  County 


77 


Feet  Inches 

the  Tarrant-Dallas  County  line.  This  is  the  top 
of  the  Woodbine  and  is  overlain  hy  Eagleford 
shale.  Between  the  two  localities  it  has  locally 
a dip  of  2 1/2°  East,  but  this  reduces  at  most 

places  to  about  1/2°  East 7 

26.  Light  yellowish  sand  with  limonitic  stain,  usually 
unconsolidated  and  containing  Ostrea  sp.  (with 

large  attachment  scar) 5 

25.  Arenaceous  yellow-brown  shales  containing  Ostrea 

sp 8 

24.  Three  ironstone  bands  interbedded  with  bluish 

sandy  shale . 2 

23.  Thin  bedded  closely  laminated  shale  with  dimension 
layers  of  iron  stained  red  shale,  and  containing 
gypsum,  limonite  and  oyster  shells  (O.  carica). 

The  lower  10  feet  is  especially  fossiliferous 22 


(The  section  in  the  cuts  west  of  this  locality 
exposes  all  of  the  foregoing  members,  and  in 
addition  in  a deep  run  about  a mile  east  of 
Tarrant,  the  following  section  is  exposed.) 

22.  Bluish  red  shale  with  limonite  stain  and  abundant 

gypsum.  Ostrea  carica  is  rare  in  the  top 20 

21.  Loosely  laminated  thin  bedded  brown  shale, 

weathering  to  a rough  faced  cliff 5 

20.  Compact  laminated  brown  shale  forming  a smooth 

cliff  face,  .i 2 

19.  Three  thin  red  ironstone  layers  with  interbedded 

compact  blue  clay 4 

18.  Bluish  limonitic  shale... 12 

(There  is  a break  in  the  section  at  this  point. 


A cut  of  the  Rock  Island  Railway  1/2  mile  east  of 
Tarrant  exposes  the  following  section.) 

16.  Thin  bedded  red  sandstone,  no  fossils  seen.  Minor 
faulting  present.  Gypsum  present.  Dip  is  2 
degrees  east  in  the  west  end  of  the  cut,  and 
straightens  out  to  1 degree  in  the  east  end.  . . .10 
15.  Blue  shales  containing  gypsum  and  lignite  seams. 

No  fossils 12 

It  is  doubtful  if  many  of  these  members  are  continuous  over 
great  areas.  There  is  a break  in  the  section  near  Tarrant  sta- 
tion. There  is  a middle  sandstone  member  of  the  Woodbine 
formation  which  consists  of  massive  red  sandstone,  and  which 
seems  extensive.  Its  structure  is  complicated  by  lenticular 


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University  of  Texas  Bulletin 


masses  and  by  sharp  reversals  of  dip.  About  2 miles  west  of 
Tarrant  station  at  the  crossing  of  the  Arlington-Grapevine  road 
and  the  Rock  Island  railway,  is  a massive  sandstone  ledge.  A 
cut  of  the  railway  2 miles  west  exposes  a similar  sandstone 
ledge.  Cuts  along  the  first  parallel  road  north  of  the  Rock 
Island  railway,  from  Birdville  to  the  county  line  and  a few 
cuts  south  of  the  railway  expose  the  lower  half  of  the  Woodbine 
formation.  There  is  locally  at  least  a basal  sandstone  which 
forms  the  resistant  cap  of  certain  “ Brushy  Knobs.”  For  ex- 
ample, on  the  knob  2 miles  northwest  of  Burleson,  the  basal 
strata  of  the  Woodbine  are  seen  to  be  in  part  a sandy  shale 
and  in  part  a red  sandstone  whose  massive  fragments  are  scat- 
tered over  the  crest  of  the  hill.  At  Burleson  this  stratum*  is  fos- 
siliferous. 

The  Woodbine  formation  in  the  Liggett-Tarrant  section  thus 
seems  to  consist  of  three  red  sandstones  and  two  interbedded 
series  of  blue  shales  with  various  other  lithologic  features.  Ex- 
tensive cross  bedding  and  some  evidence  of  large  lenticular 
masses  were  seen  in  this  section.  Sharp  reversals  of  dip  and 
rapid  tapering  of  small  lenses  so  as  to  simulate  angular  non- 
conformity within  the  formation  were  seen. 

Dip  and  thickness : The  apparent  local  dip  of  the  Woodbine 

varies  greatly,  due  to  two  factors,  cross  bedding  and  lenticular 
masses.  An  estimated  thickness  between  Handley  and  Arlington 
of  300  feet  has  been  given  by  Hill. 

This  is  based  on  a dip  of  40  feet  per  mile  of  the  overlying 
and  underlying  strata,  but  this  estimate  is  probably  too  low. 
The  uniform  maximum  dip  of  the  Washita  division  east  of  Fort 
Worth  is  2 degrees  southeast,  and  the  measured  dip  of  the 
Eagle  Ford  and  Austin  chalk  west  of  Dallas  approximate  1 
degree  southeast  A From  numerous  observations  Tarrant  and 

*The  minor  faulting  of  the  Austin  chalk  often  obscures  its 
general  dip,  but  the  following  data  indicate  the  mean  maximum  dip 
to  be  about  1 degree  near  Dallas:*  White  Rock  cliff,  cut  on  Fort 
Worth  pike,  5 miles  west  of  Dallas,  1 degree  dip,  direction  260 
degrees  from  magnetic  north.  South  end  of  Oak  Cliff  viaduct,  1 
degreen  20  minutes,  dip  in  direction  215  degrees  from  magnetic 
north.  Missouri,  Kansas  & Texas  Railway  cut,  1 mile  north  of 
Union  Terminal  Dallas,  1 degree  dip,  direction  110  degrees  from 
magnetic  north. 


Fig.  6.  Columnar  section  of  portion  of  Woodbine  formation  in  cuts 
of  Rock  Island  railway  between  Tarrant  station  and  the 
Tarrant-Dallas  county  line.  The  numbers  refer  to  correspond- 
ing strata  described  on  pp.  76-7.  Vertical  scale,  % inch 
1 foot. 


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University  of  Texas  Bulletin 


Dallas  counties  we  place  the  mean  maximum  dip  of  the  Wood- 
bine at  1 Y2  degrees  southeast,  which  counting  reversals  of 
dip  would  mean  a thickness  of  350  feet  for  the  formation. 


DIPS  OF  WOODBINE  STRATA  IN  TARRANT  AND  DALLAS  COUNTIES 


1.  Road  due  east  from 
Birdville: 


Angle  of  dip  Direction  in  degrees 
° ' from  magnetic  north 


3 

30 

90 

1 

20 

82 

5 

114  (lenticular  mass) 

1 

30 

196 

1 

245. 

2.  Rock  Island  Rail- 

way cuts  2 miles 
east  of  Tarrant 
station : 2 

3.  Bear  creek,  2 miles 

north  west  of 
Tarrant  station: 

4.  1/2  miles  south- 

west of  Grapevine:  1-3 


30  80 

30  80 

110  (with  reversals) 


Structure : The  main  relief  features  of  the  Woodbine  strip 

of  cross  timber  land  are  produced  by  the  alternating  harder  and 
softer  strata.  This  gives  an  obscured  “euesta”  topography, 
especially  near  the  outcrops  of  the  middle  and  upper  massive 
sandstones,  both  of  which  make  small  ridges  in  the  landscape. 
The  outcrop  of  the  latter  may  be  seen  along  the  Rock  Island 
railway  between  Irving  and  Tarrant  station.  Certain  harder 
ironstone  ledges  cap  the  summits  of  numerous  “Brushy  Knobs” 
which  form  outlying  strips  of  islands  often  parallel  to  the  west- 
ern border  of  the  main  Woodbine  formation.  Certain  notably 
sharp  peaks  within  the  outcrop  are  likely  due  to  lenticular  masses 
of  iron  ore. 


The  cross  bedding  and  consequent  divergence  of  dip  is  one  of 
the  most  striking  structural  features  of  the  Woodbine  sands  and 
is  purely  local  in  extent  and  not  indicative  of  underlying  dis- 
turbances of  economic  importance.  Very  striking  reversals  of 
dip  within  short  distances  are  common  features  of  the  Woodbine 


The  Geology  of  Tarrant  County 


81 


formation.  If  the  contacts  of  the  Woodbine  in  north  Texas  are 
conformable  as  reported,  then  these  variations  of  dip  within  the 
formation  must  straighten  ont  at  the  contacts.  Such  twisted 
strata  overlain  by  evenly  dipping  beds  are  seen  in  many  places. 

Even  more  deceptive  are  the  numerous  steep  or  gentle  len- 
ticular masses  which  are  underlain  and  may  be  overlain  by 
evenly  dipping  strata.  These  are  not  to  be  confused  with 
“domes”  and  indicate  no  underlying  structure  of  importance,  as 
detailed  in  the  discussion  on  possibilities  of  oil  and  gas.  A lens- 
shaped mass  with  its  slopes  will  often  closely  resemble  a dome, 
especially  if  the  mass  is  not  penertated  by  a cutting  revealing 
the  undisturbed  strata  beneath.  These  lenses  are  of  variable  size, 
often  many  hundred  feet  across. 

Small  scale  faulting  was  seen  at  many  places.  The  shallow- 
ness of  the  deposition  is  indicated  by  included  masses,  as  for 
instance  an  irregular  limestone  mass  of  about  two  cubic  feet 
surrounded  by  a sandstone  cyst  and  completely  imbedded  in  the 
Woodbine  formation.  Vertical  joint  planes  running  in  the  di- 
rection of  the  strike  were  seen  in  the  middle  sandstone  near 
Tarrant  station. 

Minerals:  The  Woodbine  sands  contain  immense  quantities 

of  low  grade  iron  oxides  which  make  up  the  bulk  of  the  strata 
at  certain  levels  and  at  others  merely  impregnate  or  discolor 
the  sandstone.  At  a few  levels  and  locally  as  in  the  basal  ar- 
gillaceous sand,  the  iron  is  extremely  low  in  percentage,  but 
such  material  burns  to  a red  brick.  A nearly  stainless  stratum 
outcrops  near  Mansfield..  Gypsum  is  present  as  broken  sheets 
and  .fragments  at  certain  levels,  as  in  the  upper  third  of  the 
formation,  and  contributes  an  unpleasant  element  to  the  water 
from  this  level.  Scattered  fragments  of  gypsum  are  seen  at 
practically  all  levels  of  the  Woodbine  formation  which  were 
examined  by  us.  Lignite  is  present  in  the  blue  shale  below  the 
middle  sandstone,  and  may  be  seen  in  the  Rock  Island  railway 
cut  east  of  Tarrant  station,  where  there  are  several  seams  each 
less  than  one  inch  thick,  and  of  no  commercial  importance.  Wood 
occurs  in  three  forms,  silicified,  lignitized,  and  practically  un- 
altered. So  far  no  other  plant  remains  occur  in  Tarrant  county 
although  they  are  reported  in  abundance  along  the  Red  River. 


t— Taft-ant 


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University  of  Texas  Bulletin 


Desert  varnish  is  a thin  enamel-like  incrustation  which  sometimes 
forms  on  the  face  of  sandstone  exposures,  especially  if  the 
sandstone  is  rich  in  iron.  The  conditions  necessary  are  that  the 
sandstone  shall  contain  a large  quantity  of  absorbed  water  to- 
gether with  a considerable  amount  or  iron  (or  manganese)  salts 
and  that  there  shall  be  an  uninterrupted  arid  spell  of  many 
weeks.  The  eapilliary  movement  of  the  water  brings  to  the 
surface  the  dissolved  salts  of  iron  and  deposits  them  in  a thin 
crust  which  is  reddish  or  yellowish  if  there  is  little  organic 
matter  and  increasingly  greenish  with  the  increased  amounts  of 
organic  substances  which  can  reduce  the  iron  oxides.  A truly 
remarkable  exhibition  of  this  phenomenon  was  observed  by  the 
writers  in  an  isolated  block  of  Woodbine  sandstone  two  miles 
southeast  of  Denton,  Texas.  Following  the  very  long  arid  spell 
of  1918,  the  “varnish”  had  formed  in  an  excavated  pit  about 
twelve  feet  across  and  about  seven  feet  deep.  The  excavation 
faced  towards  the  southwest  and  the  entire  surface,  including 
furrows  and  grooves  made  by  the  picks,  was  covered  with  a thin 
enameled  surface  of  greenish  color,  averaging  about  1/16  of  an 
inch  in  thickness.  The  green  color  was  spotted  with  darker 
green  and  blacks,  the  whole  giving  the  effect  of  the  rarest 
Turkish  tile. 

Fossils  of  the  Woodbine  formation:  The  following  fossils 

were  reported  by  Hill  in  the  21st  Ann.  Rept.,  U.  S.  G.  S.,  part 
17,  pages  314-318: 


Ostrea  soleniscus  Meek. 

Ostrea  carica  Cragin. 

Exogyra  columbella  Meek. 

Modiola  filisculpta  Cragin. 

Aguilera  cumminsi  White. 

Cytherea  leveretti  Cragin. 

Trigonarca  siouxensis  H.  & M. 

Area  gallieni  variety  tramitensis 
Cragin. 

Barbatia  micronema  Meek. 


Pteria  salinensis  White. 
Turritella  coalvillensis  Meek. 
Turritella  renauxiana  Cragin. 
Cerithium  interlineatum  Cragin. 
Natica  tramitensis  Cragin. 
Nerita  sp,  Cragin. 

Scaphites  sp.  Hill. 

Crab  sp. 

Plants  spp. 


UPPER  CRETACEOUS 


EAGLEFORD  SHALES 

Brief  Diagnosis:  The  Eagle  Ford  Shales,  the  easternmost 

formation  in  Tarrant  County,  outcrops  in  two  small  areas  which 
are  separated  by  the  alluvial  Trinity  River  valley.  The  first 


The  Geology  of  Tarrant  County 


88 


area  extends  from  near  the  northeast  corner  of  the  county  along 
an  irregular  line  through  Grapevine  and  thence  southeast  to  the 
Dallas  county  line  near  Liggett,  where  the  contact  runs  nearly 
south,  remaining  within  Tarrant  county  and  about  *4  mile  west 
of  the  county  line.  The  formation  outcrops  in  small  runs  into 
the  Trinity  almost  at  the  point  where  the  Rock  Island  railway 
crosses  the  Tarrant-Dallas  county  line.  The  contact  likewise 
runs  along  a stream,  Tradinghouse  creek,  just  east  of  Arlington. 
The  second  area  is  a roughly  triangular  strip  covering  the  south- 
east corner  of  the  county.  The  formation  consists  of  blackish 
and  bluish  shales,  with  seams  of  arenaceous  and  shelly  limestone, 
and  weathers  into  a black,  waxy,  carbonaceous,  treeless,  rolling 
upland  soil.  The  formation  is  stated  to  be  about  500  feet  thick 
between  Arlington  and  the  White  Rock  escarpment  west  of  Dal- 
las; of  this  thickness  about  half  occurs  in  southeastern  Tarrant 
county. 

Description  of  Localities:  The  Bear  Creek  locality  is  stated 
by  Taff  and  Shuler  to  show  the  contact  between  the  Woodbine 
and  the  basal  Eagleford  shales.  The  contact  is  excellently 
exposed  in  a small  run . and  in  railway  cuts  at  the  point  where 
the  Rock  Island  railway  crosses  the  Tarrant-Dallas  county  line. 
Here  the  Eagleford  is  a characteristic  laminated  blue  shale 
with  a few  arenaceous  thin  ledges  near  the  base.  Acanthoceras 
swallovi  (Shumard)  is  found  in  the  basal  three  feet.  The 
Eagleford  formation  conformably  overlies  the  Woodbine,  whose 
top  stratum  is  a laminated  sandstone  in  most  places  composed 
almost  entirely  of  masses  of  nacreous  shells.  The  upper  contact 
of  the  Eagleford  shales  does  not  occur  in  Tarrant  county  but  is 
finely  exposed  at  the  White  Rock  escarpment,  5 miles  west  of 
Dallas,  and  in  the  hills  south  of  the  Arcadia  Park  stop  on  the 
Dallas  interurban.  At  these  localities  are  found  many  shark 
teeth  and  vertebrae,  Schloenbachia  spp.,  Ostrea  belliplicata  Shu- 
mard, Inoceramus  sp.,  gastropods  and  pelecypods. 

There  are  slight  variations  in  dip  in  the  Eagleford  shales 
but  it  is  doubtful  if  these  in  Tarrant  county  indicate  any  struc- 
tures of  economic  importance  in  the  Eagleford  or  the  under- 
lying Woodbine  formations;  while  the  slight  disturbances  farther 
east  may  be  connected  with  the  local  small  scale  faulting  so 
prevalent  in  the  Austin  chalk. 


84 


University  of  Texas  Bulletin 


CENOZQIC  AND  RECENT 

The  Cenozoic  and  recent  deposits  in  Tarrant  County  are  made 
up,  as  previously  noted,  of  gravels.  The  gravels  are  readily 
divided  into  the  upland  deposits  and  the  lowland  deposits, — 
known  to  the  trade  as  “pit”  gravels  and  “stream”  gravels. 

The  distribution  and  physical  appearance  of  these  is  discussed 
on  page  91.  Besides  the  physical  appearance,  the  fossils  of 
the  two  gravels  are  of  interest.  In  both  cases  the  fossils  originate 
— except  for  the  rare  vertebrate  forms, — in  older  formations. 
The  lowland  gravels  contain  the  fossils  of  the  beds  through  which 
the  streams  pass,  being  predominantly  of  the  upper  part  of  the 
geological  section  in  the  south  and  east  and  of  the  lower  part 
of  the  section  in  the  west  and  north.  The  upland  gravels 
contain  fossils  which  are  consistently  of  the  Fredericksburg 
formations.  In  both  types  of  gravel  certain  fossils  are  readily 
recognized,  the  various  species  of  Grypheas  and  the  small  sea 
urchin,  Hemiaster,  being  well  preserved,  although  badly  worn. 
The  few  vertebrate  remains  which  have  been  found  occur  in  the 
upland  gravels.  Among  these  are  the  Mammoth  (Elephas  im- 
perator)  of  which  a splendid  tusk  and  a few  teeth  are  on  ex- 
hibition in  the  Carnegie  Library  at  Fort  Worth;  a mastodon; 
Elephas,  small  species,  and  Megatherium,  bothfrom  a gravel 
pit  in  the  river  bank  one  mile  east  of  the  Court  House,  where 
many  Pleistocene  fossils  have  been  found;  and  a small  horse, 
believed  to  be  Equus  francisii,  of  which  only  the  teeth  have 
been  found.  Shells  of  clams  (Quadrula  spp.),  snails  and  other 
fresh  water  invertebrates  are  common  just  below  the  Lake 
Worth  dam,  on  the  uplands  and  elsewhere.  The  distribution 
of  the  upland  gravels  indicates  that  they  may  be  older  than 
the  Pleistocene,  but  the  authors  have  not  entered  into  the  broad 
problems  connected  with  these  deposits. 

ECONOMIC  GEOLOGY 

The  nature  of  the  underlying  rocks  of  Tarrant  county,  deter- 
mines to  a great  extent  its  natural  resources  and  possibilities 
and  indicates  its  logical  line  of  future  development.  Geology 


The  Geology  of  Tarrant  County  85 

explains  many  of  the  resources  and  natural  advantages  of  a 
region,  and  among  them  the  following: 

(1)  Resources  of  location:  Substratum,  drainage,  accessibility, 

varieties  of  topography,  scenery. 

(2)  Resources  of  soil:  Adaptability  to  different  kinds  of  use; 

farm  land,  grazing  land,  etc. 

(3)  Resources  of  native  or  importable  plant  and  animal  life,. 

(4)  Resources  of  crude  material:  Building  material,  road  ma- 

terial, minerals,  oil  and  gas,  artesian  water. 

RESOURCES  OF  LOCATION 

Excavation  and  foundations.  The  question  of  the  safety 
hardness,  resistance,  and  thickness  of  the  underlying  rocks  bears 
directly  upon  excavation  for  deep  foundations  of  large  buildings, 
or  for  pipe  lines,  drainage  lines,  sewers,  cuts,  dams,  bridges  and 
other  structural  works. 

This  question  is  of  significance  where,  as  under  Fort  Worth, 
a rather  thin  cap  rock  is  succeeded  by  a marl  member  which 
not  only  is  soft  but  is  water  bearing  and  caves  readily.  The 
solid  Fort  Worth  limestone  under  the  business  district  of  the 
city  averages  about  25  feet  in  thickness.  If  this  is  not  mostly 
excavated  out  for  basements  and  sub-basements,  it  of  course 
affords  a firm  substratum  for  buildings  up  to  a certain  size, 
depending  upon  the  amount  of  the  excavation.  When  this  25 
feet  of  limestone  is  penetrated  a marl  mixed  with  insecure  thin 
limy  ledges  and  extending  downward  for  about  15  feet  is  en- 
countered. This  level  may  be  instantly  recognized  by  the 
abundant  brachiopod,  Kingena,  which  the  excavation  will  reveal. 

Then  comes  a limy  ledge  about  7 feet  thick  with  considerable 
marl  material  intermixed.  This  ledge  has  firmness  enough  for 
many  building  purposes. 

Underneath  is  a series  of  limy  and  marl  layers  of  increasing 
firmness  and  compactness,  which  after  11  feet  below  the  ledge 
are  quite  compact  and  afford  an  excellent  foundation.  The  sec- 
tion may  be  seen  in  Plate  6,  and  is  exposed  at  several  places 
near  the  court  house. 

The  marlier  layers  have  a certain  water  content  which  will 
depend  somewhat  on  whether  their  outcrops  west  and  north  of 


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the  site  of  excavation  have  a favorable  catchment  area  or  not. 
If  they  are  narrow  or  built  over  or  paved,  or  slope  sharply  to 
the  west,  less  water  will  seep  under  the  foundation. 

The  foundations  of  numerous  buildings  in  Fort  Worth  have 
penetrated  these  strata  to  different  depths.  An  example  is  the 
foundation  of  the  W.  T.  Waggoner  office  building  whose  exca- 
vation (May  1919)  sectioned  at  Eighth  and  Houston  streets 
about  two  feet  of  soil,  then  penetrated  the  typical  thin  bedded 
Fort  Worth  limestone,  which  towards  the  base  was  bluish,  cal- 
careous and  very  hard.  The  interbedding  was  a hard  calcareous 
marl.  The  excavation  for  concrete  piles  was  continued  to  stratum 
1 which  lay  at  a distance  of  28  feet  below  the  level  of  the  side- 
walk. In  general  it  is  inadvisable  to  base  heavy  buildings  on 
marl. 

Roads  and  railroads.  Roads  in  many  parts  of  the  county  have 
a naturally  firm  sub-stratum-,  as  over  portions  of  the  Fort  Worth 
and  Mainstreet  uplands.  The  Woodbine  roads  often  have  a 
natural  base,  and  along  the  eastern  border  the  Eagle  Ford  over- 
wash forms  a clay  binder  for  the  sand  and  makes  an  excellent 
natural  roadbed. 

The  railroads  running  in  the  strike  of  the  Comanchean  for- 
mations often  lie  on  limestone  strata,  as  the  Frisco  on  the  min- 
eralized ledge  (17)  of  the- Duck  Creek  formation,  southwest  of 
Fort  Worth.  The  Misouri,  Kansas  and  Texas  and  the  Interna- 
tional and  Great  Northern  run  successively  on  the  Fort  Worth 
limestone,  the  Weno  limestone  and  the  Mainstreet  limestone 
south  of  Fort  Worth.  The  Santa  Fe  south  of  Fort  Worth  in 
Tarrant  County  runs  on  the  Mainstreet  limestone.  Railroad 
cuttings  across  the  strike  follow  more  or  less  the  * ‘ cuesta  ’ ’ slopes, 
as  the  Texas  and  Pacific  to  the  west  and  the  Interurban  to  Dallas. 

Drainage.  The  streams  have  cut  back  the  softer  materials 
from  the  adjoining  harder  formations  producing  small  and  poor 
exposures  of  the  marly  material.  This  is  especially  true  of  the 
Grayson  marl,  where  good  exposures  are  rarely  found,  and  which 
only  exceptionally  weathers  as  a divide,  such  as  that  southeast  of 
Burleson,  or  in  stream  cuts  descending  from  the  Woodbine  for- 
mation. The  softer  nature  of  the  Grayson  marl  is  attested  by  the 


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disproportionate  number  of  graveyards  scattered  throughout 
its  outcrop  across  Tarrant  county. 

Certain  railroads  run  on  drainage  divides,  as  the  Fort  Worth 
and  Denver  City  Railway,  which  north  of  Fort  Worth  follows 
the  divide  between  the  West  Fork  and  the  Denton  Fork  of  the 
Trinity. 

Slumping  and  side-slip  of  strata  on  the  edge  of  uplands 
result  in  virtual  reversals  of  dip  and  in  two  known  places  blocks 
of  Fort  Worth  limestone  have  been  undermined  by  the  Trinity. 

RESOURCES  OF  SOIL 

No  soil  map  of  Tarrant  county  has  appeared,  but  analagous 
conditions  resulting  from  the  same  types  of  geology  may  be 
seen  in  the  maps  of  Grayson  and  Travis  counties.  The  county 
contains  soil  areas  which  follow  closely  the  outcrop  of  the  geo- 
logical formations  as  mapped  here,  and  these  may  be  roughly- 
divided  as  follows: 

(1)  Uplands : The  Fort  Worth  and  Mainstreet  uplands  have 
been  stated  to  possess  such  shallow  soil  that  they  are  suitable 
only  for  grazing.  However  over  great  stretches,  notably  the 
dip  plain  area  north  of  Fort  Worth,  which  Hill  calls  the  type 
of  the  Black  Prairie,  the  soil  and  subsoil  are  deep  and  are  used 
for  large  scale  farming.  The  exposures  of  the  Fort  Worth 
limestone  southwest  of  the  city  are  extensively  used  for  graz- 
ing. These  uplands  drain  quickly,  even  after  heavy  rains,  and 
in  general  artificial  water  basins  must  be  constructed  if  a per- 
manent water  supply  is  desired.  This  portion  of  the  county 
is  dissected  by  streams  cutting  down  to  the  Trinity,  especially 
near  the  western  prairie  border,  and  is  rolling  or  slightly  hilly 
and  almost  treeless.  Practically  the  same  conditions  hold  for 
the  Mainstreet  upland  except  that  near  its  eastern  border  there 
is  a considerable  mixture  of  red  sandy  soil  from  Woodbine 
overwash.  The  two  uplands  are  at  many  places  connected  by 
a fairly  even  grassy  slope  obscuring  the  intervening  formation 
and  making  the  two  areas  practically  one  topographic  unit. 

(2)  River  Bottom.  The  untimbered  portion  of  the  alluvial 
Trinity  River  valley  is  wide  enough  in  many  places  to  permit 


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of  considerable  cultivation  and  in  the  central  and  western  part 
of  the  county  is  not  subject  to  serious  overflow.  In  the  eastern 
part  of  the  county  a system  of  levees  exists.  The  river  alluvium 
is  deep  and  has  at  many  places  a gravel  and  sand  foundation 
which  is  exploited  commercially,  as  at  the  Rock  Island  pits  near 
Birdville.  This  material  is  transported  by  the  stream  for  con- 
siderable distances  as  seen  by  the  Fredericksburg  fossils  occur- 
ring in  gravel  deposits  near  Dallas.  The  numerous  Exogyra 
texana  and  Grypkea  mwcoui  in  these  gravels  come  mostly  from 
strata  below  and  outcropping  west  of  the  white  Goodland  lime- 
stone. As  the  river  cuts  thru  the  Woodbine  cross  timbers  the 
^oil  deposits  gather  sandy  acidic  components,  so  that  this  por- 
tion of  the  bottom  land  like  the  Woodbine  is  used  for  fruit 
growing. 

(3)  Woodbine  Gross  Timbers : This  strip  of  red  sandy 
acidic  soil  is  still  densely  timbered  with  black  jack  and  post 
oak,  but  contains  natural  glades  and  artificially  cleared  areas. 
The  soil  is  suitable  for  many  purposes,  especially  fruit  growing, 
peaches,  peanuts,  and  to  a less  extent  cotton,  corn  and  to- 
bacco. However  its  limitations  should  be  clearly  noticed  if 
loss  is  to  be  avoided  in  the  selection  of  crops.  The  Fort  Worth 
region  has  been  agriculturally,  first  a cattle  raising  country,  and 
second  a grain  and  cotton  country.  Without  doubt  its  diverse 
soils  are  suited  to  a variety  of  profitable  special  products  whose 
exploitation  is  only  a matter  of  study  and  experiment.  The 
main  cotton  belt  at  present  is  the  outcrop  of  Eagle  Ford  (and 
to  a less  extent  the  Woodbine  also)  in  the  eastern  part  of  the 
county. 

RESOURCES  OF  NATIVE  OR  IMPORTABLE  PLANT  AND 
ANIMAL  LIFE 

As  already  stated  the  county  lies  at  the  junction  of  the  humid 
(eastern)  and  the  semi-arid  (western)  divisions  of  the  Lower 
Austral  Zone,  and  it  has  accordingly  a mixture  of  temperate 
and  subtropical  wild  life.  This  is  seen  clearly  in  the  mammals, 
birds,  insects,  and  in  the  plants.  Subtropical  and  temperate 
zone  birds  live  side  by  side  in  the  upper  Trinity  valley,  as  noted 


The  Geology  of  Tarrant  County 


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bv  Bendire.  The  county  lies  on  the  northern  range  of  certain 
subtropical  insects  and  other  invertebrates.  Finally  the  same 
situation  is  true  of  other  vertebrates. 

A plant  zone  map  of  Texas  as  indeed  of  most  of  the  United 
States  will  correspond  broadly  to  a map  of  the  underlying  geo- 
logical systems.  Hill  and  others  have  recognized  that  the  vari- 
ous divisions  of  the  Texas  Oomanchean  and  Cretaceous  carry 
their  own  peculiar  or  at  least  prevailing  flora;  and  the  pheno- 
menon of  timber  belts  which  characterize  certain  formations  has 
long  been  known.  This  correspondence  extends  for  some  plants 
to  the  minute  subdivisions  of  geological  formations. 

There  are  certain  plants  which  occur  either  largely  or  ex- 
clusively upon  certain  types  of  topography  regardless  of  the 
underlying  geological  formation. 


1)  UPLAND  PLANTS 


Centaurea  americana. 
Helianthus  annuus. 
Helianthus  maximiliani. 
Lindheimera  texana. 
Castilleja  purpurea. 
Linum  lewisii. 

Linum  arkansana. 
Polygala  alba. 

Croton  texensls. 
Euphorbia  marginata. 
Baptisia  bracteata. 
Psoralea  hypogaea. 


Callirhoe  digitata. 
Megapterium  missouriense. 
Phellopterus  macrorhizus. 
Eustoma  russellanium. 
Amsonia  texana. 

Quamasia  hyacinthea. 
Cooperia  drummondi. 
S'isyrhinchium  amoenum. 
Lesquerella  gracilis. 

Draba  cuneifolia. 

Neptunia  lutea. 


(2)  ESCARPMENT  PLANTS 

Yucca  arkansana  (mainly  on  Fredericksburg  limestone). 
Androstephium  ceruleum  (mainly  on  Duck  Creek  limestone). 
Erythronium  albidum  coloratum  (mainly  on  Duck  Creek  limestone). 
Aragallus  lamberti. 


(3)  LOWLAND  PLANTS 

Smilax  bona-nox.  Viola  obliqua. 

Clematis  simsii.  Viola  raflnesquii 

Cnidosculus  texanus.  Oraetegus  mollis. 

(4)  PLANTS  OF  THE  WOODBINE  SANDSTONE  BELT 

Quercus  marylandicus  the  “Black  Jack”  oak  is  the  characteristic  tree  of 
the  “lower  cross  timbers.” 

Pentstemon  australis.  Houstonia  minima. 


RESOURCES  OF  CRUDE  MATERIAL 
LIMESTONE  INDUSTRIES. 

When  mention  is  made  of  the  resources  suggested  by  the 
geology  of  a region,  the  average  layman  assumes  at  once  that 
reference  is  made  to  mining  possibilities  and  to  oil  and  other 


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so-called  mineral  resources.  Often  a region  has  undeveloped 
resources  in  its  rocks  which  are  of  more  permanent  value  than 
even  fairly  rich  mineral  deposits  in  the  popular  sense. 

Limestone  industries  are  many,  and  much  depends  on  the 
various  factors  of  the  quality  of  the  limestone,  the  presence 
or  absence  of  other  substances  besides  the  calcium  carbonate 
which  makes  up  the  bulk  of  all  limestone,  transportation  fa- 
cilities, accessibility  to  a market,  fuel,  labor,  etc.  Examples 
of  limestone  industries  are:  quarries,  cement  plants,  carbon- 

dioxide  gas  plants,  rock  crushers  and  lime  kilns.. 

The  limestones  in  Tarrant  county  which  offer  possibilities  in 
the  opinion  of  the  writers  are  as  follows : the  Mainstreet  lime- 
stone, which  is  fifty  feet  thick;  the  Weno  limestone,  which  is 
twenty  feet  thick;  the  Duck  Creek  limestone,  which  is  thirty 
feet  thick;  and  the  Coodland  limestone  which  is  a little  more 
than  one  hundred  feet  thick.  The  areal  extent  of  each  of  these 
at  the  surface  can  be  seen  on  the  map. 

Unfortunately  very  little  exploitation  of  these  various  lime- 
stones has  been  carried  beyond  the  experimental  stage.  Even  in 
the  simple  matter  of  crushed  rock  for  road  metal,  the  writers 
lack  any  practical  data  based  on  industrial  experience,  as  Tar- 
rant county  has  the  crushed  rock  for  its  roads  shipped  from 
another  county. 

The  following  considerations  govern  the  limestones  of  * the 
county:  Only  one,  the  Weno  limestone  offers  possibilities  for 
the  establishment  of  quarries.  This  excellent  material  is  rather 
limited.  The  rock,  however,  seems  to  cleave  well  and  should 
be  adapted  to  .exploitation  as  a good  grade  of  building  stone. 
It  is  white  in  color,  fine  grained  in  texture,  does  not  contain 
enough  iron  to  be  likely  to  develop  wall  stains,  and  as  noted 
above  cleaves  well,  with  the  cleavage  planes  clean  and  parallel. 
Blocks  to  a maximum  thickness  of  eighteen  inches  should  be 
Readily  obtained  and  with  a length  of  six  feet  and  a breadth 
of  three  feet.  As  this  limestone  is  in  many  places  covered 
with  other  formations  or  otherwise  in  a condition  to  make  a 
quarry  impracticable,  the  following  localities  are  suggested  to 
^prospectors : the  area  north  of  Polytechnic  especially  in  the 

region  near  the  Texas  and  Pacific  tracks,  the  bluffs  along  Syca- 


The  Geology  of  Tarrant  County 


91 


more  creek  especially  in  the  neighborhood  of  the  crossing  of 
the  loop  road  about  a mile  after  it  leaves  the  Burleson  road. 
A considerable  area  of  this  limestone  is  exposed  along  the  Keller 
road  about  four  miles  north  of  Fort  Worth,  but  much  of  the 
exposure  is  overlain  by  a thick  blanket  of  soil. 

The  Mainstreet  limestone  is  the  best  exposed  over  a large 
area,  but  is  massive,  breaking  into  angular  fragments  and  con- 
siderably iron  stained.  In  the  opinion  of  the  writers,  however, 
this  limestone  should  be  entirely  satisfactory  for  erushed  rock. 
It  i,s  remarkably  uniform  through  a considerable  thickness,  and 
this  is  a quality  desirable  in  crushed  rock.  The  Fort  Worth 
limestone  and  the  Duck  Creek  limestone  contain  much  marl  in 
the  form  of  beds  alternating  with  the  limestone.  In  the  present 
stage  of  development  of  the  limestone  industries  these  two 
limestones  are  not  likely  to  be  worth  exploiting  as  long  as  there 
is  such  a large  supply  of  much  higher  grade  material. 

The  Goodland  limestone  offers,  apparently,  more  possibilities. 
The  map  indicates  the  great  area  covered  by  this  formation.  The 
region  around  Benbrook  is  especially  rich  "in  good  exposures  of 
this  limestone.  The  most  conspicuous  single  exposure  of  this 
limestone  is  in  the  bluff  at  the  north  end  of  the  Lake  Worth 
dam.  In  fact  the  use  of  this  limestone  in  connection  with 
the  construction  of  this  dam  seems  to  be  the  only  extensive  ex- 
periment which  has  been  made  in  its  exploitation. 

The  Goodland  limestone  is  almost  pure  calcium  carbonate, 
and  offers  possibilities  for  exploitation  in  many  ways : lime 

kilns,  carbon  dioxide  plants,  cement  plants  (using  the  Kiamitia 
clays  immediately  overlying  the  Goodland  limestone).  For 
practical  purposes  the  supply  may  be  considered  as  inexhausti- 
ble and  many  excellent  exposures  occur  near  the  city  of  Fort 
Worth. 

GRAVEL  AND  SAND 

There  are  two  types  of  gravel  in  Tarrant  county : 

(a)  River  gravel,  lowland,  rounded,  clean,  little  cementing  or 
adhering  of  sand  or  clay. 

(b)  Pit  gravel,  upland,  angular,  cemented  with  matrix  of 
poorly  assorted  particles  of  sand,  clay,  rock  materials,  etc.,  of 
various  sizes. 


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The  lowland  gravel  occurs  at  or  near  the  present  level  of  the 
drainage  at  many  places  even  up  the  small  laterals.  The  up- 
land gravel  is  widely  distributed  and  is  worked  commercially. 
There  are  considerable  deposits  along  the  whole  course  of  the 
Trinity  particularly  the  Clear  Fork,  on  the"  south  side  of  the 
Arlington  Heights  divide,  on  the  hills  around  the  Texas  Chris- 
tian University,  on  the  Rock  Island  railway  south  of  Birdville, 
and  along  Sycamore  Creek,  Big  and  Little  Bear  Creeks  apd 
Big  and  Little  Fossil  Creeks. 

SAND : The  river  sands  are  impure,  being  mixed  with  clay, 
gravel  and  calcareous  particles  and  fragments.  The  purest  sands 
are  probably  in  the  upper  part  of  the  Woodbine  near  Mans- 
field. This  is  a round-grained  sand,  and  has  some  iron  stain. 
Extensive  sands  occur  in  the  Walnut  and  Paluxy  formations  west 
and  northwest  of  Fort  Worth. 

MINERALS : The  following  have  been  found  in  Tarrant 

County:  Calcite,  aragonite;  pyrite,  hematite,  limonite;  celes- 

tite ; gypsum ; radidlarian  ooze ; desert  varnish.  In  addition 
gilsonite  in  the  Trinity  sand,  and  lignite  in  the  Woodbine  occur 
in  non- workable  amounts.  Apparently  none  is  of  economic 
importance. 

CLAY  INDUSTRIES 

Probably  the  purest  clays  in  the  county  are  those  of  the 
Pawpaw  and  Woodbine  formations;  which,  so  far  as  known,  have 
not  been  tested  except  for  brick.  There  are  also  clay  members 
in  the  Paluxy  sand.  These  clays  are  iron  stained  and  somewhat 
impure,  but  should  be  suitable  for  tile,  crockery,  earthenware, 
and  certain  other  clay  products.  The  Athens  Pottery  Company 
at  Fort  Worth  ships  in  its  clay.  The  availability  of  clay  for 
commercial  use  depends  somewhat  upon  the  price  of  fuel  and 
the  conditions  of  transportation.  Factories  will  locate  in  a 
great  rail  center  like  Fort  Worth  and  ship  in  their  raw  material. 
Hence  it  is  extremely  desirable  to  use  all  possible  local  raw 
material,  and  to  make  special  investigations  to  find  which  are 
suitable.  There  has  apparently  been  little  testing  and  no  ex- 
ploitation in  Tarrant  county  but  the  favorable  combination  of 


The  Geology  of  Tarrant  County 


93 


materials  found  here  makes  a greater  future  development  of 
certain  clay  industries  seem  very  probable. 

BRICK 

The  general  requirements  for  the  location  of  a brickyard  are 
accessibility  to  transportation,  to  fuel,  to  suitable  market,  to 
water,  and  to  crude  material  as  described.  The  crude  material 
should  be  present  in  large  quantities ; should  be  accessible  with- 
out great  amounts  of  excavation ; should  be  free  from  overlying 
soil  or  undesirable  rock  formations  which  would  require  re- 
moval; should  be  capable  of  proper  drainage;  and  should  be  of 
a certain  quality  or  purity,  especially  as  regards  shell  material 
or  other  calcareous  inclusions. 

Evidently  several  formations  exposed  in  Tarrant  county  fit 
these  conditions,  especially  the  following:  Eagle  Ford  shales, 
Woodbine  sands  (basal  part),  Pawpaw  clays,  Weno  marl, 
Kiamitia  marl  Paluxy  sands,  Walnut  clays.  These  are  exploited 
so  far  at  only  five  places  in  Tarrant  county,  but  it  will  be  useful 
to  refer  to  the  nearly  similar  conditions  found  in  the  same 
formations  in  adjoining  counties.  In  this  connection  attention 
is  called  to  the  interesting  geological  possibilities  of  brick  yards 
to  students  or  others  doing  paleontological  work,  since  in  brick- 
yards marl  formations,  otherwise  poorly  exposed,  are  well  sec- 
tioned. 

As  the  pits  deepen  the  question  of  drainage  becomes  more 
pressing.  Many  pits  are  pumped,  a proceedure  involving  ex- 
pense and  often  delay.  It  might  be  practicable  in  some  pits  to 
resort  to  the  drainage  device  used  at  times  by  the  American 
Expeditionary  Forces  in  France,  in  which  a lower  lying  dry 
sand  was  reached  by  boring  and  the  drainage  emptied  automati- 
cally into  this  sand.  In  the  Washita  divisions,  certain  levels 
of  the  Paluxy  sand  might  be  drilled  to ; and  above  the  Washita, 
certain  of  the  Woodbine  sands. 

CLAYS  OF  THE  WOODBINE  SANDS 

Acme  Brick  yards,  one  mile  south  of  Denton,  Texas:  The 

material  used  is  mainly  a whitish  arenaceous  clay  layer  whose 
base  lies  within  25  feet  of  the  bottom  of  the  Woodbine  forma- 
tion. This  layer  is  nearly  30  feet  thick  and  is  overlain  by  a 


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University  of  Texas  Bulletin 


lenticular  mass  of  red  sandstone  which  is  dragged  back  from 
the  top  preceding  excavation  of  the  material.  This  whitish  ma- 
terial is  semi-consolidated  in  places  and  weathers  nearly  white 
with  little  iron  stain.  The  “red  clay”  burnt  alone  gives  a non- 
spotted  building  brick;  the  white  material  alone  gives  a cream 
colored  brick;  while  the  two  mixed  give  a spotted  de  luxe  brick 
which  is  sorted. 

J ohnson  Station,  Tarrant  County : This  brick  yard  uses 

material  from  the  lower  third  of  the  Woodbine  sands. 

Kennedale,  Tarrant  county : two  brickyards  use  the  middle 
part  of  the  Woodbine  sands. 

Brambleton,  Tarrant  county:  this  brickyard  uses  middle 

Woodbine  material. 

CLAYS  OF  THE  PAWPAW  AND  WENO  FORMATIONS 

The  Cobb  Brick  yards,  Fort  Worth,  use  two  sources  of  sup- 
ply,  the  basal  Weno  marl  and  the  Pawpaw  clay.  The  pit  in 
the  Weno  near  Sycamore  Creek  exposes  nearly  the  basal  third 
of  the  marl,  including  the  Gervilliopsis  layer.  The  marl  after 
weathering,  is  grayish-blue,  putty  colored  and  is  only  slightly 
shelly.  The  few  Gryphea , Gervilliopsis  and  other  shells  present 
after  screening  are  burned  with  the  mixture  and  reduce  to  in- 
significant friable  limy  spots.  This  Weno  marl  burns  at  about 
1700° F to  a variety  of  red  bricks,  which  are  sorted.  The  upper 
Pawpaw  marl  east  of  Sycamore  Creek  is  used  to  produce  a red 
building  brick  which  burns  at  about  1700°F.  The  clays  of  the 
Pawpaw  formation  in  Tarrant  County  offer  many  advantages 
for  brickmaking.  They  are  particularly  free  from  shells,  ob- 
viating screening,  as  is  necessary  in  certain  clays  of  the  Weno 
deposits.  The  formation  has  in  the  basal  portion  small  pyrite 
fossils  whose  contained  sulphur  might  be  a disadvantage,  but 
the  total  amount  of  this  material  is  small. 

The  Pawpaw  formation  is  a homogeneous  clay  or  shale  prac- 
tically free  from  calcareous  shells,  about  23-27  feet  thick.  It  is 
capped  at  most  places  by  Mainstreet  limestone  which  would 
have  to  be  blasted  or  stripped  back.  This  Mainstreet  cap  at 
places  disintegrates  so  that  the  stripping  is  easier;  however,  at 
such  places  it  contaminates  by  percolation  the  underlying  clay 
to  a depth  of  3 feet  or  more.  The  drainage  of  Pawpaw  localities 


The  Geology  of  Tarrant  County 


95 


is  almost  invariably  good,  since  they  lie  on  hillsides.  For  the 
same  reason  a gravity  haul  to  a plant  located  so  as  to  utilize  also 
the  underlying  Weno  marl  is  practicable.  The  amount  of  ma- 
terial is  unlimited,  since  it  is  necessary  only  to  follow  the  line 
of  outcrop.  This  23-27  feet  of  Pawpaw  is  underlaid  by  an 
amount  of  Weno  limestone  which  it  would  be  impracticable  to 
remove,  in  order  to  expose  the  underlying  Weno  marl.  It 
should  be  noted  that  north  of  the  Trinity,  the  Pawpaw  contains 
immense  amounts  of  siliceous  fragments  resembling  jasper, 
which  will  probably  require  screening;  this  material  is  absent 
south  of  the  Trinity.  Finally,  in  Tarrant  County  the  forma- 
tion is  accessible  to  railroads. 

BRICKYARDS  1%  MILES  SOUTHEAST  OF  GAINESVILLE,  TEXAS 

The  pit  of  the  Gainesville  Brick  Co.  exposes  the  Weno  forma- 
tion from  the  Quarry  limestone  group,  which  is  well  developed 
on  the  south  rim  of  the  pit  down  to  the  basal  third  of  the 
formation,  about  20  feet  below  the  Gervilliopsis  layer.  The 
Weno  is  about  75  feet  thick  and  the  depth  of  the  pit  practically 
the  same.  A water  well  nearby  penetrated  the  Denton  marl 
and  the  Fort  Worth  limestone. 

A “buff  marl”  layer,  free  from  shells  and  lying  about  2 feet 
below  the  Gervilliopsis  layer  burns  to  a clear  buff  brick  and  is 
much  fayored.  If  the  material  is  excessively  shelly  it  is  dis- 
carded. Much  material  from  the  upper  part  of  the  pit  also 
was  discarded  on  account  of  the  abundant  ironstone.  The  burn- 
ing temperatures  vary  from  1700°F.  to  1800°F.,  and  the 
bricks  are  sorted.  The  plant  uses  the  dry  moulding  process,  is 
equipped  to  burn  lignite  and  coal,  and  has  a capacity  of 
40,000  bricks  per  day. 

CLAYS  OF  THE  PALUXY  SANDS 

One  brickyard  north  of  the  Texas  & Pacific  Railway  on  the 
White  Settlement  road  15  miles  west  of  Fort  Worth,  uses  the 
material  from  the  upper  part  of  the  Paluxy  formation,  which 
burns  to  a red  building  brick. 

POSSIBILITIES  OF  OIL  AND  GAS 

A bulletin  on  the  geology  of  any  of  the  counties  of  North 
Texas  would  be  incomplete  and  unsatisfactory  without  a dis- 


96 


University  of  Texas  Bulletin 


cussion  of  the  possibilities  of  petroleum.  Mr.  E.  W.  Shaw,  of 
the  U.  S.  Geological  Survey,  included  Tarrant  County  in  his 
study  of  the  natural  gas  resources  of  parts  of  North  Texas, 
(U.  S.  G.  S.  Bulletin  629),  including  a structural  maj  of  the 
outcrop  of  certain  limestone  ledges  in  the  area  south  and  west 
of  Benbrook.  It  was  his  opinion  that  notwithstanding  the  fact 
that  oil  and  gas  showings  in  water  wells  of  the  southern  part 
of  Tarrant  County  are  frequent  it  is  likely  that  the  accumula- 
tions of  petroleum  products  in  the  rocks  underlying  this  county 
has  escaped.  The  writers  of  this  bulletin  are  inclined  to  agree 
with  this  general  view.  We  do  not  pretend  to  have  thoroughly 
investigated  all  the  structural  possibilities  in  the  county,  and 
it  is  of  course  possible  that  structures  favorable  for  the  con- 
centration and  retention  of  oil  or  gas  may  exist.  HowTever, 
we  have  seen  no  such  structures,  and  the  probable  occurrence 
of  a large  syncline  in  the^  Paleozoic  rocks  in  this  region  is  es- 
pecially unfavorable. 

In  Tarrant  County,  as  in  many  other  counties  of  North 
Texas,  considerable  exploratory  drilling  has  been  carried  on 
in  the  area  covered  by  the  Woodbine  formation.  The  red  sand- 
stone which  makes  up  the  formation,  is  extremely  interesting 
and  complex.  Its  exact  thickness  is  not  known,  and  a complete 
recorded  section  does  not  exist.  It  is  much  cross  bedded  and 
its  dip  changes  with  frequent  and  startling  suddenness.  Above 
all  else,  it  has  extremely  deceptive  structural  features  in  the 
shape  of  lens-like  masses.  Some  cf  these  are  quite  extensive, 
and  might  very  well  be  mistaken  for  “domes”  suggesting  a 
corresponding  structure  in  the  underlying  rocks  and,  of  course, 
the  possibility  of  concentration  of  petroleum.  A careful  study 
of  one  of  these  bodies  has  been  made  by  the  winters.  Unfor- 
tunately this  body  does  not  occur  in  Tarrant  County,  but  it  is 
so  perfectly  exposed  and  the  arguments  of  the  writers  are  so 
well  illustrated  that  attention  is  called  to  one  of  these  bodies  in 
the  Acme  Brick  Yards  at  Denton,  Texas,  In  the  westward 
facing  out  of  the  pit,  a little  more  than  forty  feet  of  the  Wood- 
bine formation  is  exposed.  The  upper  fifteen  feet  is  made  up 
of  a iens-like  mass,  containing  four  members.  The  lens  shape 
is  due  to  sharply  dipping  members  in  the  bed.  The  dip  here 


The  Geology  of  Tarrant  County 


97 


is  mainly  south.  About  a thousand  yards  north  of  the  pit  in 
the  cut  of  the  Missouri.  Kansas  and  Texas  Kailway  is  an  ex- 
posure of  the  rocks  in  the  plane  of  the  pit,  in  which  the  mem- 
bers dip  in  the  opposite  direction.  In  both  cases,  the  under- 
lying: rocks  are  horizontal.  This  pseudo  “dome”  then  is  esti- 
mated to  have  had  an  original  depth  of  from  sixty  to  seventy 
feet  and  a diameter  of  nearly  a mile,  and  without  the  under- 
lying horizontal  beds  so  well  exposed,  this  “dome”  might  have 
been  discovered  and  exploited  by  some  inexperienced  pefson. 

The  Bend  and  the  Ellenburger  formations,  if  present  under- 
neath Tarrant  County,  are  deeply  buried.  The  Bend  has  not 
been  reached  in  the  Polytechnic  well  at  4380  feet  according  to 
Dr.  Udden.  A sample  said  to  be  from  this  well  from  “below 
4,000  feet”  (depth  not  stated,  possibly  near  4,600  feet)  is  a 
hard  black  shale  lacking  fossils;  and  a sample  claimed  to  be 
from  “about  4,600  feet”  is  likewise  black  shale,  probably  not 
Bend,  but  resembles  somewhat  the  black  shale  above  the  Bend, 
in  the  opinion  of  Dr.  Udden.  Comparison  of  wells  at  George- 
town, Gatesville,  Myra,  and  Muenster  with  those  in  Tarrant 
County  would  appear  to  indicate  a considerable  depression, 
possibly  synclinal,  of  the  Trinity,  and  the  Bend  and  Ellen- 
burger if  present,  under  the  Fort  Worth  region;  there  is  also 
a feeble  reflection  of  this  depression  in  the  overlying  Coman- 
chean  formations. 

The  following  table  gives  approximate  data  for  contouring 
the  base  of  the  Trinity  sand  in  Tarrant  County;  it  indicates 
that  the  base  of  the  Trinity  here  dips  almost  east  at  the  rate  of 
about  48  feet  per  mile. 


WELL 

Altitude 

BASE  OF 

TRINITY 

See 

of  well 

Depth 

Altitude 

page 

Tucker’s  Hill  Well . . . . 

650 

1120 

- 495 

25 

Polytechnic  Well 

1250? 

- 600? 

25,107 

Mansfield  Well 

1678 

-1078 

115 

Grapevine  Well 

1720? 

-1120? 

7— Tarrant 


98 


University  of  Texas  Bulletin 


WATER  RESOURCES 

The  water  supply  of  Tarrant  County  is  derived  from  (a) 
streams,  (b)  artesian  wells,  (c)  dug  wells  and  (d)  seepage 
springs;  of  these  the  first  two  named  produce  the  greater  part 
of  the  supply.  The  various  city  reservoirs  on  the  two  forks 
of  the  Trinity,  especially  the  Lake  Worth  reservoir,  have  been 
widely  discussed  and  will  not  be  treated  here.  The  problem  of 
impounded  water  is  in  Tarrant  County  mainly  an  engineering 
problem,  since  a supply  is  assured.  Much  water  is  still  derived 
from  artesian  sources,  mainly  by  pumping.  The  principal  ar- 
tesian reservoirs  under  Tarrant  County  are  the  Woodbine,  which 
is  a shallow  source  of  water  underlying  the  strip  of  country  east 
of  Handley;  the  Paluxy  reservoirs,  which  underly  the  whole 
County  except  a small  area  in  the  northwest  corner;  and  the 
Trinity  reservoir,  which  underlies  the  whole  county.  Since 
all  these  reservoirs  dip  to  the  southeast  they  increase  in  depth, 
and  the  pressure  of  their  waters  increases,  going  either  south 
or  east.  Accordingly,  as  younger  strata  come  in  on  top  of 
them  towards  the  east  border  of  the  county  they  will  be  overlain 
at  increasing  depths,  as  seen  in  the  following  table  of  approx- 
imate depths. 

This  table  gives  the  approximate  depths  at  which  the  various 
artesian  water  reservoirs  occur  in  Tarrant  County.  The  points 
taken  to  illustrate  these  depths  to  the  various  water  reservoirs 
are  Mansfield,  Texas,  the  Texas  and  Pacific  Railway  Station  at 
Arlington,  Texas  (elevation  616  feet),  the  Central  Fire  Station, 
Fort  Worth,  Texas  (elevation  620  feet),  The  Polytechnic  and  the 
Tucker’s  Hill  wells,  East  Fort  Worth  (elevation  650  feet).  The 
figures  are  only  approximate.  The  notation  of  Dr.  R.  T.  Hill 
is  used,  the  shallowest  horizon  in  each  formation  being  listed 
first  and  the  deepest  last.  Trinity  1 is  the  main  Trinity  reser- 
voir. 


The  Geology  of  Tarrant  County  99 


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2 

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zn 

"L 

03 

X 

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£ 

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£ £ 

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fl  ta 

03  .2 

£ 

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Eh 

Ph  o M 

ELEVATION  OF  SURFACE,  in  feet:  575 

616 

650 

650 

620 

DEPTH  TO: 
Woodbine  2 

70 

Woodbine  1 

235 

Woodbine-Washita 

contact  150 

300 

Goodland-Washita 

contact  500 

659 

124 

257 

122 

Walnut 

360 

244 

Paluxy  2 

670 

750? 

300 

476 

378 

Paluxy  1 

740 

425 

503 

Glenrose 

950 

893 

1042 

963 

Trinity  3 

1454 

1480? 

895 

1100 

875 

Trinity  2 

1480 

1035 

1015 

Trinity  1 

1533 

1120? 

1280?1100? 

Paleozoic  contact 

1550 

1580? 

1120? 

1297? 

The  Woodbine  contains  at  least  two  reservoirs,  varying  some- 
what but  at  places  in  Tarrant  County  about  100  feet  apart. 
These  are  shallow  and  feebly  developed  over  the  Woodbine  out- 
crop in  Tarrant  County,  and  are  available  at  moderate  depths 
under  the  Eagle  Ford  prairies.  There  is  a water  bearing  stratum 
in  the  base  of  the  Fredericksburg  limestone,  possibly  formed  by 
the  shell  conglomerate  20  feet  above  the  base,  as  already  men- 
tioned. 

The  basal  hard  rock  and  shell  conglomerate  of  the  Walnut 
clays  encloses  the  topmost  Paluxy  water  bed,  as  may  be  seen  in 
numerous  exposures  in  the  western  part  of  the  county.  The 
Paluxy  contains  clay  seams  interstratified  with  the  red  sand 
layers,  and  these  clays  act  to  retain  the  Paluxy  water  in  the 
water  sands. 

'The  Glenrose  limestone,  which  is  invariably  arenaceous  in 
parts,  contains  one  or  more  artesian  water  beds.  The  most  im- 
portant and  purest  artesian  water  in  the  county  comes  from  the 
Trinity  reservoir  which  consists  of  three  main  sands.  These 
are  interstratified  mainly  by  impermeable,  water-tight  clays, 
and  lie  at  approximately  the  depths  indicated.  (See  also  well 
logs,  pp.  107  ff.) 


100 


University  of  Texas  Bulletin 


DIP,  ALTITUDES,  ETC. 

DIP 

The  dip  of  the  formations  is  for  mast  parts  of  the  county 
very  nearly  2°  southeast.  The  influence  of  this  amount  of  dip 
in  the  formation  of  parallel  outcrops  has  been  mentioned  in 
connection  with  the  decreased  altitude  of  the  geological 
younger  outcrops,  which  lie  toward  the  east.  (p.  9). 

Thickness  of  beds  for  Dip  of  2°,  in  directions  of  various  angles 
to  the  dip. 

This  table  will  apply  to  most  outcrops  in  Tarrant  County. 
The  angles  given  are  azimuths  read  in  a clockwise  direction  from 
the  magnetic  north,  which  is  here  taken  as  being  10°  east  of 
the  true  north. 


Magnetic 

Slope  for  2°  Dip 

Slope  for  2° 

Dip 

Azimuth 

Ft.  per  100 

Ft.  per  mile 

5° 

+1.75 

+ 92.4 

20 

.87 

45.9 

35 

0.00 

00.0 

STRIKE 

50 

-0.87 

- 45.9 

65 

-1.75 

- 92.4 

80 

-2.62 

-138.3 

95 

-2.91 

-153.6 

110 

-3.20 

-169.0 

125 

-3.49 

-184.3 

/ DIP 

140 

-3.20 

-169.0 

TO  SOUTHEAST 

155 

-2.91 

-153.6 

170 

-2.62 

-138.3 

185 

-1.75 

- 92.4 

200 

-0.87 

- 45.9 

215 

0.00 

00.0 

STRIKE 

230 

+0.87 

+ 45.9 

245 

1.75 

92.4 

260 

2.62 

138.3 

275 

2.91 

153.6 

290 

3.20 

169.0  . 

305 

3.49 

184.3 

DIP 

320 

3.20 

169.0 

335 

2.91 

153.6 

350 

2.62 

138.3 

The  last  two  columns  give  the  amount  to  he  added  to  or  subtracted 


The  Geology  of  Tarrant  County 


101 


from  the  elevation  of  a station  to  find  the  elevation  of  the  same 
stratigraphic  level  at  another  station  which  is  the  given  distance 
and  direction  away. 

The  following  is  a list  of  altitudes  within  the  county,  all  of 
which  are  from  the  records  established  by  the  United  States 
Geological  Survey  and  by  the  City  Engineer’s  Office,  Fort 
Worth : 

ALTITUDES  IN  TARRANT  COUNTY 

620.0  Bench  mark,  U.  S'.  G.  S.,  brass  plug  in  ledge  above  sidewalk, 

northeast  corner  Fire  Department,  Throckmorton  and  8th 
streets,  Fort  Worth. 

619.0  BM,  U.  S.  G.  S.,  base  of  Jennings  Avenue  viaduct. 

670.0  BM,  U.  S.  G.  S.  Weather  Bureau,  Fort  Worth. 


614.0  Track,  T.  & P.  Ry.  station,  Fort  Worth. 

602.0  Track,  Santa  Fe  station,  Fort  Worth. 

594.0  Top  of  spillway,  Lake  Worth  dam. 

692.93  Northeast  curb,  corner  College  and  Capps  avenues. 

558.0  Santa  Fe  station  at  Stock  Yards,  North  Fort  Worth: 

627.18  Spike  on  pole,  northeast  corner  Forest  Ave.  and  Edwin  St. 

618.19  Concrete  bridge,  south  end  Forest  Park,  2-inch  iron  pipe  in 

northeast  corner  pier. 

631.72  Spike  in  light  pole,  northwest  corner  Forest  Park. 

672.62  Spike  in  telephone  pole,  northwest  corner  Gibson  Ave.  and 
Forest  Park  Blvd. 

582.52  Culvert  under  car  line  near  southeast  corner  Forest  Park, 
top  southwest  corner  of  culvert. 

616.3  H.  & T.  C.  rail  at  crossing  of  H.  & T.  C.  under  I.  & G.  N. 

track,  near  Sycamore  creek,  3 miles  southeast  of  court- 
house. 

616.0  Arlington,  T.  & P.  Ry.  track. 

845.0  Avondale,  F.  W.  & D.  Ry.  track  at  station. 

658.0  Benbrook,  T.  & P.  Ry.  station. 

694.0  Bethel,  M.  K.  & T.  track. 

535.0  Grapevine,  St.  L.  S.  W.  track. 

590.0  Handley,  T.  & P.  track. 

700.0  Haslet,  Santa  Fe  track. 

704.0  Keller,  M.  K.  & T.  track. 

603.0  Kennedale,  H.  & T.  C.  track. 

580.0  Mansfield,  H.  & T.  C.  track. 

773.0  Primrose,  Frisco  track. 

724.0  Saginaw,  Santa  Fe  track. 

606.0  Watauga,  M.  K.  & T.  track. 


102 


University  of  Texas  Bulletin 


934.0  Webb. 

558.0  Fort  Worth,  crossing  of  St.  L.  S.  W.  Ry. 

606.0  BM  at  crossing  of  Ft.  W.  & D.  C.  Ry.  and  Ft.  W.  & D. 

electric  line. 

533.0  North  Fort  Worth,  St.  L.  S.  W.  station. 

627.0  Hodge,  St.  L.  S.  W. 

606.0  Hodge,  M.  K.  & T. 

606.0  Hodge,  crossing  of  M.  K.  & T.  and  St.  L.  S.  W. 

618.0  Arlington,  BM  on  Citizens’  National  Bank. 

579.0  Handley,  BM  on  Power  House  of  N.  T.  T.  Co. 

PRECISE  LEVELS  IN  TARRANT  COUNTY  AND  A 
FEW  NEARBY  POINTS1 


Feet 

841.255 


751.311 


628.168 


Meters 
256.415  O 


229.000  P 


191.466  Q 


Avondale,  Tarrant  County,  Texas,  6 feet 
south  of  the  third  telegraph  pole  south 
of  and  across  the  tracks  from  railroad 
station,  and  30  feet  from  the  tracks,  in 
line  with  the  telegraph  poles.  Bottom 
of  a square  hole  cut  in  the  top  of  a 
Texas  limestone  post  lettered  US  BM. 

1 *4  miles  north  of  Saginaw,  Tarrant 
County,  Texas,  on  an  arched  concrete 
abutment  of  the  Chicago,  Rock  Island 
and  Pacific  Railway,  four  telegraph  poles 
north  of  mile  pole  10  of  the  Fort  Worth 
and  Denver  City  Railway,  on  the  east 
side  of  the  abutment,  in  the  northeast 
corner,  9 inches  from  either  edge.  In- 
tersection of  two  lines  cut  in  end  of  half- 
inch copper  bolt. 

About  1V2  miles  north  of  the  Trinity 
River  crossing  at  Fort  Worth,  Tarrant 
County,  Texas,  in  the  northwest  corner 
of  the  west  side  of  an  arched  concrete 
culvert  at  mile  post  608  (Chicago,  Rock 
Island  and  Pacific  Railway  track)  8 


1 Bowie  and  Avers;  Fourth  general  adjustment  of  the  precise 
level  net  in  the  United  States  and  the  resulting  standard  eleva- 
tions. U.  S.  Coast  and  Geodetic  Survey,  Special  Publication  18, 
1914,  pp.  108,  120,  151,  235-6. 

Hayford:  Precise  leveling  in  the  United  States  1900-1903 

with  a readjustment  of  the  level  net  and  resulting  elevations.  U. 
S.  Coast  and  Geodetic  Survey,  Appendix  No.  3,  Report  for  1903, 
Washington,  1917,  pp.  782-3. 


The  Geology  of  Tarrant  County 


103 


Feet 


537.640 


530.380 


569.467 


605.865 


619.254 


Meters 


163.873  R 


161.660  S 


173.574  T 


184.668  U 


188.749  V 


inches  from  the  north  and  4 inches  from 
the  west  edge.  Intersection  of  two  lines 
cut  in  end  of  half-inch  copper  bolt. 

About  3 miles  north  of  Union  Station  at 
Fort  Worth,  Texas,  on  a large  stone  pier 
(the  first  from  the  north  bank  of  Trinity 
River)  of  the  Chicago,  Rock  Island  and 
Pacific  Railway  bridge  No.  3306,  on  the 
northwest  corner  of  the  west  side,  8 
inches  from  either  edge.  Bottom  of 
square  hole  cut  in  stone. 

About  2 miles  north  of  Union  Station  at 
Fort  Worth,  Texas,  on  the  south  end  of 
the  west  pier  supporting  the  Missouri*. 
Kansas  and  Texas  track  (over  the  Chi- 
cago, Rock  Island  and  Pacific  Railway 
track)  at  the  north  end  of  the  freight 
yards  of  the  Chicago,  Rock  Island  and 
Pacific  Railway,  on  the  lowest  step  at  the 
southeast  corner,  6 inches  from  either 
edge.  Bottom  of  square  hole  cut  in 
stone. 

A mile  north  of  Union  Station  at  Fort 
Worth,  Texas,  on  the  northwest  corner 
of  the  large  block  forming  the  lowest 
step  to  the  west  side  of  the  south  abut- 
ment supporting  the  Fort  Worth  and 
Denver  City  Railway  track  (over  the 
Chicago,  Rock  Island  and  Pacific  track), 
4 inches  from  the  adjacent  edges  of  the 
stone  and  3 y2  feet  from  the  ground. 
Bottom  of  square  hole  cut  in  stone. 

Fort  Worth,  Texas,  at  the  west  side  of  the 
south  abutment  where  the  railroad 
tracks  pass  over  the  Fort  4Worth  and 
Dallas  Electric  Line  tracks  (2  blocks  east 
of  Union  station)  on  the  second  step 
from  the  top,  6 inches  from  the  adjacent 
edges  of  stone.  Bottom  of  square  hole 
cut  in  stone. 

Fort  Worth,  Texas,  at  the  northeast  corner 
of  the  city  fire  department  building  (cen- 
tral station)  on  Throckmorton  street,  be- 
tween Eighth  and  Ninth,  near  the  center 
of  the  east  face  of  a block  of  stone  in 


104 


University  of  Texas  Bulletin 


Feet 


578.391 


617.935 


618.749 


654.884 


770.773 


044.585 


Meters 


176.294  W 


188.347  X 


188.595  M3 


199.609  N3 


234.932  O3 


287.910  Pa 


the  fourth  tier  and  about  4 feet  from 
the  ground,  15  inches  from  the  corner 
of  the  building,  13  inches  from  a win- 
dow. Cross  on  a half-inch  copper  bolt. 
(This  is  the  same  station  as  the  first 
elevation  given). 

Handley,  Tarrant  County,  Texas,  in  the 
center  of  the  middle  pilaster  on  the 
northeast  side  of  the  power  house  of  the 
Northern  Texas  Traction  Company,  about 
4 feet  from  the  ground.  Cross  on  half- 
inch copper  bolt. 

Arlington,  Tarrant  County,  Texas,  at  the 
east  side  of  the  north  face  of  the  Citi- 
zens’ National  Bank  Building,  in  the 
middle  brick  of  the  eastern  brick  column, 
about  41/2  feet  from  the  ground.  Cross 
in  half-inch  copper  bolt. 

Fort  Worth,  Texas,  on  top  of  the  stone  base 
to  one  of  the  iron  supports  to  the  viaduct 
over  the  tracks,  one-fourth  mile  west  of 
Texas  and  Pacific  Railway  station.  The 
mark  is  on  the  base  under  the  second 
support  east  in  second  row  north  of  main 
track,  at  southeast  corner,  3 y2  inches 
from  south  and  east  edges.  Bottom  of 
square  hole  cut  in  stone. 

A mile  east  of  Belt  Junction,  Tarrant 
County,  Texas,  15  paces  from  the  eighth 
telegraph  pole  west  of  milepost  3 on 
Fort  Worth  and  Rio  Grande  Railroad,  on 
the  southwest  corner  of  the  west  abut- 
ment of  a culvert.  Bottom  of  square 
hole  cut  in  stone. 

Primrose,  Tarrant  County,  Texas,  five  poles 
west  of  the  station  sign,  six  telegraph 
poles  east  of  milepost  12,  in  an  angle  of 
the  right-of-way  fence,  on  the  Fort 
Worth  and  Rio  Grande  Railroad,  16 
paces  nbrth  of  the  track.  Bottom  of 
square  hole  cut  in  top  of  limestone  post, 
lettered  US  BM. 

Virgile,  Tarrant  County,  Texas,  10  feet 
north  of  the  third  pole  west  of  the  sta- 
tion sign,  in  an  angle  of  the  right-of-way 


The  Geology  of  Tarrant  County 


105 


Feet 


1045.109 


682.328. 


715.064 


624.392 


557.262 


Meters 

fence  on  the  Fort  Worth  and  Rio  Grande 
Railway,  15  paces  north  of  the  track. 
Bottom  of  square  hole  cut  in  top  of  lime- 
stone post,  lettered  US  BM. 

318.550  Q3  In  Parker  County,  Texas,  just  across  the 
county  line  from  Cresson.  Tarrant 
County,  Texas,  50  paces  east  of  the  sta- 
tion, 5 paces  east  of  mile  post  25,  and 
20  paces  north  of  the  track  of  the  Fort 
Worth  and  Rio  Grande  Railroad.  Bot- 
tom of  square  hole  in  top  of  limestone 
post,  lettered  US  BM. 

207.974  T3  One-half  mile  north  of  the  siding  at  Bethel, 
Tarrant  County,  Texas,  50  feet  west  of 
the  railroad  track,  in  the  right-of-way 
of  the  Missouri,  Kansas  and  Texas  main 
line,  3 feet  east  of  telegraph  pole  op- 
posite mile  post  7 64.  Bottom  of  square 
hole  in  top  of  limestone  post,  marked 
US  BM. 

217.952  U3  Burleson,  Johnson  County,  Texas,  in  the 
brick  building  used  as  the  postoffice,  in 
the  east  front,  4 % feet  above  the  side- 
walk, in  a panel  north  of  the  northern- 
most window.  Cross  in  top  of  copper 
bolt. 

190.315  Cio.  At  Fort  Worth,  Tarrant  County,  Texas,  on 
the  Hill  Street  concrete  viaduct,  over  the 
Texas  & Pacific  and  the  Frisco  Line  Rail- 
way tracks,  1.1  miles  west  of  the  Union 
Passenger  station,  on  the  east  face  of  the 
north  side  of  the  arch  over  the  main-line 
track  of  the  Texas  & Pacific  Railway,  1.45 
meters  above  the  ground  and  0.36  meter 
from  the  south  edge  of  the  face  of  the 
arch. 

169.854  D10.  2.1  miles  west  of  Fort  Worth,  Tarrant  Coun- 

ty, Texas,  on  the  highway  bridge  carrying 
the  Fort  Worth  and  Weatherford  road 
over  the  Clear  Fork  of  the  Trinity)  River, 
on  the  top  of  the  south  wing  wall  of  the 
east  concrete  abutment,  about  0.20  meter 
from  the  footplate  of  the  truss.  This 
bridge  is  about  35  meters  north  of  the 
Texas  & Pacific  Railway  bridge  249-A 
over  the  same  stream. 


106 


University  of  Texas  Bulletin 


Feet 

576.160 


623.290 


662.669 


787.285 


980.303 


888.049 


892.032 


Meters 
175.614  E10. 


189.979  F10. 


201.982  G10. 


239.965  H10. 


298.797  Iao. 


270.678  J10. 


271.892  K10. 


About  4.5  miles  west  of  Fort  Worth,  Tarrant 
County,  Texas,  and  midway  between  the 
Texas  & Pacific  Railway  track  and  the 
center  of  the  Fort  Worth  and  Weather- 
ford highway,  0.5  meter  inside  and  south 
of  the  railroad’s  right-of-way  fence  and 
1.5  meters  inside  and  east  of  the  fence  of 
the  first  by-road  that  crosses  the  track 
west  of  the  siding  for  the  Fort  Worth 
waterworks  pumping  station. 

About  1.4  miles  east  of  Benbrook,  Tarrant 
County,  Texas,  on  the  middle  pier  of  the 
Texas  & Pacific  Railway  plate-girder 
bridge  254-C  over  Marys  Creek,  on  the  top 
of  the  coping  of  the  north  end  of  the  pier, 
and  approximately  in  the  center  of  the 
stone. 

At  Benbrook,  Tarrant  County,  Texas,  on 
land  belonging  to  Mr.  C.  W.  Carpenter,  at 
the  turn  of  the  Fort  Worth  and  Weather- 
ford highway,  just  across  the  road  and 
south  of  the  Texas  & Pacific  Railway 
stock  pens,  about  50  meters  south  of  the 
main-line  track,  and  0.75  meter  south  and 
0.75  meter  west  of  the  highway  fence. 

About  2.8  miles  west  of  Benbrook,  Tarrant 
County,  Texas,  on  the  Texas  & Pacific 
Railway  plate-girder  bridge  258-B  over 
Walnut  Creek,  on  top  of  the  north  end  of 
the  east  masonry  abutment. 

At  Iona,  Parker  County,  Texas,  about  130 
meters  west  of  the  section  house,  15 
meters  south  of  the  west  end  of  the  sid- 
ing, and  1 meter  north  of  the  fence  be- 
tween the  railroad  right-of-way  and  the 
county  road. 

At  Aledo,  Parker  County,  Texas,  on  land 
belonging  to  Mr.  J.  J.  Sears  and  in  use  as 
a public  park,  about  midway  of  the  south 
side  of  the  park,  and  1 meter  north  of  the 
boundary  fence. 

At  Aledo,  Parker  County,  Texas,  on  the 
west  side  of  the  entrance  of  the  stone 
building  owned  by  Mr.  J.  J.  Sears,  and 
occupied  by  his  general  merchandise 
store,  and  2 meters  above  the  sidewalk. 


The  Geology  of  Tarrant  County  107 

DESCRIPTION  OF  NEW  MAGNETIC  STATION 

United  States  Coast  and  Geodetic  Survey  Magnetic  Station  on 
the  grounds  of  Texas  Christian  University,  Port  Worth,  Texas.  In 
the  southwest  part  of  the  grounds  of  Texas  Christian  University, 
4 miles  southwest  of  the  old  (1888)  station  and  about  3%  miles 
southwest  of  the  Courthouse,  800  feet  west  of  the  steps  of  Brite 
Bible  College  and  51.4  feet  east  of  the  west  fence  about  the  Uni- 
versity grounds,  ahd  about  85  feet  west  southwest  of  the  banks  of 
a ditch  through  this  part  of  the  grounds.  Marked  by  a limestone 
post  5"x7"x30",  projecting  2". 


Bronze  disk  dated  1918,  set  in  top. 

9°27.4'  East 
62°35.3' 
97°22.0' 
32°42.4' 


Declination 

Dip 

Longitude 

Latitude 


True  bearings:  Chimney  near  middle  of  (Rivercrest)  Country 

Club:  25°18.3'  West  of  North.  Wooden  water'tank,  1 mile  dis- 
tant: 46°58.9'  East  of  South. 

LOG  OF  WELL  AT  POLYTECHNIC,  TEXAS 


Kind  of  Material 


Shaley  soil 
Shale,  blue 
Shale  


Shale 


Mud  - 

Shale 

Shale 

Shale  - 

Shale 

Shale 


Water  sand 

Shale  

Water  sand 
Shale  


Water  sand  

Shale  

Lime  

Shale  

Lime  


Lime  shell 

Shale  

Shale  

Lime  

Shale  

Lime  

Shale  


1 i 

Feet 

[Thick 

Color 

Hardness 

From 

| To 

ness 

Formations 

Light 

0 

25 

25 

Main  street. 

Blue 

_ 

25 

118!  93 

Pawpaw. 

Gray 

Hard 

118 

128 

10 

Weno.  and 

Denton 

Blue 

— 

128 

165 

37 

Fort  Worth 

Blue 

165 

206 

41 

Duck  Creek, 

Gray 

206 

210 

4 

Kiamitia,  and 

White 

_ 

210 

291 

80 

Goodland 

Brown 

291 

297 

6 

Gray 

297 

345 

48 

Brown 

— 

345 

360 

15 

3W 

400 

40 

Walnut 

Light  gray 

400 

319 

19 

4iy 

455 

34 

Gray 

455 

476 

21 

476 

492 

16 

Paluxy 

Light  gray 

492 

510 

18 

Gray 

f 

510 

518 

8 

Gray 

Soft 

518 

526 

8 

Gray 

526 

653 

27 

Hard 

653 

563 

10 

Gienrose 

Gray 

563 

585 

22 

Blue 



585 

615 

30 

Gray 

615 

644 

29 

Blue 



644 

650 

6 

White 

650 

705 

5o 

Blue 



705 

709 

• 

108 


University  of  Texas  Bulletin 


Kind  of  Material 

Color 

Hardness 

F< 

From 

3et 

To 

Thick 

ness 

Formations 

Gray 

Blue 

709 

715 

6 

Shal«  . ..  _ . 

715 

717 

2 

Gray 

Gray 

Blue 

717 

756 

39 

Shale 

756 

790 

34 

790 

796 

6 

Gray 

796' 

822 

26 

822 

824 

2 

White 

824 

830 

6 

Shale  --  

Dark  blue 

Soft 

830 

843 

13 

Gray 

843 

857 

14 

857 

885 

28 

Shale 

Blue 

885 

893 

8 

893 

913 

Gray 

913 

935 

22 

Wofpr  sand  .. 

935 

950 

15 

shale 

Blue 

950 

956 

6 

White 

Sandy 

956 

963 

7 

963 

995 

32 

Shale  _ . 

Red 

995 

1000 

5 

1000 

1005 

5 

Shale  

Red 

995 

1000 

5 

1000 

1005 

5 

Conglomerate  of  green,  dark 
blue,  white  and  red  putty, 

1015 

1025 

10 

1015 

1025 

10 

Sand  fitnne 

1025 

1030 

5 

Trinity 

Rhale 

Red 

1030 

1047 

17 

Rand  rock 

1047 

1057 

10 

Shale 

Dark  blue 

1057 

1070 

13 

Shale 

Dark  blue 

1070 

1074 

4 

Shale  

Red 

1074 

1100 

26 

Watp.r  sand 

1100 

1125 

25 

Shale  

5 Green  and) 
jdark  blue  J 
(White  andl 
land  red  J 

1125 

1132 

Putty 

1132 

1150 

IS 

White  rock  and  sandstone— 

1150 

1180 

30 

Sand  with  particles  of  coal  . 

1180 

1190 

10 

Shale  and  Rand 

Dark  brown 

1190 

1200 

10 

MTSSTNG 

1200 

1297 

97 

Shale  

Blue 

1297 

1416 

119 

Pennsylvanian 

Tiime.Rtonp 

White 

1416 

143H 

14 

Shale  

Blue 

1430 

1168 

38 

Tame  _ _ ..  _ . 

Hard 

1468 

1475 

Shale 

Blue 

1475 

1490 

15 

r.imp  _ . _ 

Hard 

1490 

1505 

15 

Shale  

Blue 

1505 

1530 

25 

Sand 

Hard 

1530 

1550 

20 

Shale  

Blue 

• 1550 

1565 

15 

Lime  

Hard 

1565 

1570 

5 

Shale 

White 

1570 

1590 

20 

Time  . . ._  ... 

Hard 

1590 

1630 

40 

Shale 

Blue 

1630 

1638 

8 

Time 

Hard 

1638 

1646 

8 

Shale. 

Blue 

1646 

1670 

24 

Time 

Hard 

1670 

1700 

30 

Shale  _ 

Brown 

1700 

1715 

15 

Sand  hrnken  with  Rhale 

1715 

1740 

25 

Time  and  Rhale 

1740 

1775 

35 

Slate  _ 

Blue 

1775 

1800 

25 

Time 

White 

1800 

1825 

25 

Rhale 

Blue 

1825 

1840 

15 

Tiime.Rt.nne 

1840 

1845 

6 

Shale 

Blue 

1845 

1860 

15 

The  Geology  of  Tarrant  County 


109 


Kind  of  Material 

Color 

Hardness 

From 

F< 

To 

jet 

ness 

Thick 

Formations 

Hard 

1860 

1880 

20 

Shale  _ . _ 

Blue 

1880 

1890 

10 

Sand 

1890 

1915 

25 

Shale 

Blue 

1915 

1925 

10 

1925 

1935 

10 

Shale  __  .. 

Blue 

1935 

1990 

55 

Hard 

1990 

2005 

15 

Shale 

Blue 

2005 

2020 

15 

Slate  

Black 

Soft 

2020 

2040 

20 

Lime  _ 

2040 

2048 

8 

Blue 

2048 

2070 

22 

Hard 

2070 

2080 

10 

Shale 

Blue 

2080 

2120 

40 

Limestone 

2120 

2135 

15 

Shale  

Blue 

2135 

2170 

35 

Time  ..  

Hard 

2170 

2180 

10 

Shale 

2180 

2235 

55 

Chalk  rock  

2235 

2255 

20 

Shale  . 

Blue 

2255 

2270 

15 

Sand  

2270 

2280 

10 

Shale  

Blue 

2280 

2320 

40 

T.ime  _ _ 

Gray 

2320 

2340 

20 

Sand 

2340 

2360 

20 

Shale  

2360 

2375 

15 

Lime. 

Gray 

2375 

2395 

20 

Sand  rock 

Gray 

2395 

2415 

20 

Shale 

Black 

2415 

2500 

85 

Shell  rock  _ 

2500 

2550 

50 

Salt  water  and  sand  with  gas 

and  shale 

Blue 

2550 

2615 

65 

Lime  rock  shale 

Blue 

2695 

2725 

30 

Shale  rock  and  salt  water 

shale  - 

Gray 

2725 

2780 

55 

Lime  and  shale 

Black 

2825 

2900 

75 

Shale  and  lime  rock,  black 

sand,  sand  contained  oil; 

at  30001  ft.  a flow  of  salt 

JBlack  and( 

water 

(brown  ) 

2900 

3000 

100 

MISSING  

3900 

3962 

Shale  

Dark  blue 

3962 

4071 

109 

Shells  of  slate  and  lime,  with 

9 ft.  shale  between  _ 

Gray 

Hard 

4071 

4083 

12 

Shale  with  frequent  shells  of 

lime  formation 

Dark  gray 

4083 

4141 

58 

Lime,  sharp  

Dark  gray 

Hard 

4141 

4151 

10 

Slate  ___  ___  . 

Black 

4151 

4154 

3 

Lime  shell 

Black 

4154 

4159 

5 

Sandy  lime  

Black 

Sharp 

4159 

4214 

55 

Lime  

Black 

Very  hard 

4214 

4217 

3 

Shale  

Light  gray 

4217 

4295 

78 

Lime  shell  

Black 

Hard 

4295 

4298 

3 

Shale  with  shells  of  lime 

Dark  gray 

4298 

4333 

35 

Lime  

Black 

Medium 

4333 

4339 

6 

Lime  

Black 

Very  hard 

4339 

4342 

3 

Sand  (no  water) 

Gray 

Hard,  sharp 

4342 

4352 

10 

Sand  

Gray 

Coarse 

4352 

4355 

3 

Shale  _ 

Dark 

4355 

4363 

8 

Shale  

Black 

4363 

4371 

8 

Shale  with  shells  of  lime 

Black 

4371 

4409 

35 

Shale,  with  frequent  hard 

shells  of  lime 

Black 

— 

4409 

4470 

61 

110 


University  of  Texas  Bulletin 


DESCRIPTION  OF  SAMPLES  FROM  THE  POLYTECHNIC  WELL 
BETWEEN  THE  DEPTHS  OF  2,495  FEET  AND  4,380  FEET,  BY 
DR.  J.  A.  UDDEN: 


Dark,  almost  black  shale  of  fine  texture,  and  considerable 
hardness.  Very  little  silt  present.  On  heating  in 
tube,  faint  fumes  of  sulphur  and  exceptionally  strong 


fumes  of  ammonia  were  noted.  Shale  no  doubt  Penn- 
sylvanian . 2 495  ft. 

Dark  shale  with  some  fragments  of  exceedingly  fine  sand- 
stone, both  showing  very  minute  scales  of  mica.  Penn- 
sylvanian in  aspect.  No  fossils  noted ...2500  ft. 


Dark,  almost  black,  shale  which  shows  a few  scattered  minute 
fragments  of  black  carbonaceous  material.  No  fossils 
noted.  Heated  in  closed  tube  it  gives  off  very  strong 
fumes  of  ammonia,  and  in-distinct  fumes  of  bitumen 
and  sulphur.  Aspect  Pennsylvanian  2520  ft. 

Dark  gray  shale,  with  a trace  of  very  fine-grained  sand  and 
some  very  small  mica  scales.  On  heating  in  closed 
tube,  it  gives  strong  fumes  of  ammonia,  and  darkens. 

No  fossils  noted.  Pennsylvanian  in  aspect 2540  ft. 

Dark  gray  indurated  shale,  with  a few  fragments  of  red  shale 
and  some  white  calcareous  small  fragments.  Gives 
strong  fumes  of  ammonia  when  heated.  The  calca- 
reous fragments  may  have  fallen  in  from  above.  Penn- 
sylvanian   2560  ft. 

Very  dark  bluish  gray  shale  of  hackly  fracture.  On  heating 
it  gives  weak  fumes  of  sulphur  and  very  strong  fumes 
of  ammonia.  Some  fragments  of  white  limestone 
noted,  evidently  from  above.  No  fossils  noted  of  any 
kind.  Pennsylvanian  . 2570  ft. 

Dark  gray  stony  shale,  non-calcareous,  very  slightly  mica- 
ceous, and  gives  weak  fumes  of  sulphur  and  strong 
fumes  of  ammonia.  No  fossils  noted.  Pennsylvanian . 2575  ft. 

Very,  dark  gray  shale,  somewhat  indurated,  slightly  micace- 
ous with  streaks  of  silt,  which  are  more  micaceous 
than  the  finer  and  darker  shale.  Strong  fumes  of 
ammonia  noted  on  heating-.  No  fossils  found.  Non- 


calcareous.  Pennsylvanian  2588  ft. 

Mostly  dark  gray  sandy  silt  with  some  sandstone.  The  sand- 
stone is  cemented  by  calcareous  material.  Some  mica 
present  in  shiny  particles.  Ammonia  noted  on  heating 
in  closed  tube.  No  foraminifera  present 2600  ft. 

Bluish  dark  gray  sandy  shale.  Strong  ammonia  smell  given 
off  from  sample  when  heated  in  closed  tube.  Sand 
grains  plentiful.  No  foraminifera  noted 2640  ft 


The  Geology  of  Tarrant  County 


111 


A hard,  dark  blue  shale  with  lumps  of  brownish-pink  clay. 
Ammonia  noted  when  heated  in  closed  tube.  No  fora- 
minifera  noted.  Some  sand  grains  present.  Typical 
Pennsylvanian  2685  ft. 

Gray,  non-calcareous  shale,  of  fine  texture,  bluish  when  wet. 

When  heated  in  closed  tube,  the  sample  gives  off 
strong  ammonia  fumes  and  bitiminous  fumes.  Frag- 
ments decrepitate  in  flame.  One  piece  of  brownish, 
hard,  non-calcareous  clay  noted 2706  ft. 

Gray,  non-calcareous  shale  of  fine  texture.  Heated  in  tube, 
the  samples  gives  off  strong  fumes  of  ammonia  and 
some  bituminous  fumes.  There  are  some  angular 
grains.  Fragments  decrepitate  in  flame 2730  ft. 

Bluish  gray,  non-calcareous  shale  of  fine  texture.  When 
heated  in  closed  tube,  the  sample  throws  off  decided 
fumes  of  ammonia,  but  bituminous  fumes  are  absent. 
Decrepitation  marked  2760-2770  ft. 

Bluish  gray  non-calcareous  shale  of  fine  texture,  with  a few 
pieces  of  brownish,  hard,  non-calcareous  clay.  Heated 
in  tube  the  sample  gives  strong  ammonia  fumes  2760-2770  ft. 

Gray  shale,  non-calcareous.  The  sample  contains  considerable 
sand.  No  pyrite  or  mica  noticed.  Heated  in  closed 
tube  it  gives  strong  fumes  of  ammonia,  but  no  bitu- 
minous fumes.  Fragments  decrepitate  in  flame .... 

Very  dark  and  hard  shale  of  uniform  texture  with  a few  frag- 
ments of  clay-iron-stone.  In  closed  tube  it  gives  off 
strong  fumes  of  ammonia  and  faint  fumes  of  sulphur. 

No  fossils  noted  2830  ft. 

Very  hard  dark  shale  with  some  fragments  of  concretionary 
non-calcareous  indurated  material.  Heated  in  closed 
tube  gives  off  strong  fumes  of  ammonia  and  sulphur 
fumes.  No  fossils  noted  2835  ft. 

Dark  blue  hard  shale.  Heated  in  closed  tube  sample  gives 

off  fumes  of  sulphur  and  ammonia 2890  ft. 

Dark,  almost  black,  hard  shale  and  light  gray  sandstone  of 
fine  texture  cemented  by  calcareous  material.  Pyrite 
noted.  Bituminous  fumes  and  strong  fumes  of  am- 
monia given  off  in  closed  tube.  Crinoid  stems  and  a 
crinoid  spine  noted  . . . 2895  ft. 

Light  gray  sandstone  of  fine  texture  and  dark  shale.  Bitu- 
minous fumes  and  fumes  of  ammonia  given  when 
heated  in  tube.  No  fossils  noted 2905  ft. 

Dark  shale  and  light  gray  sandstone.  The  sandstone  is  fine 
grained,  and  with  interstices  partly  open  and  partly 
filled  with  calcareous  material.  Faint  fumes  of  bitu- 
men and  ammonia.  No  fossils  2915  ft. 


112 


University  of  Texas  Bulletin 


Dark  shale  and  sandstone.  Heated  in  open  tube  gives  bitu- 
minous fumes  and  slight  ammonia  fumes.  The  sand- 
stone is  very  slightly  infiltrated  with  lime.  No  fos- 
sils noted  # 2920  ft. 

Dark  hard  shale.  Heated  in  tube  the  sample  gives  very 

Strong  fumes  of  ammonia.  No  fossils 2980  ft. 

Light  gray  sand  and  some  fragments  of  blue  shale,  and  cal- 
careous material.  The  sand  has  a dirty  yellow  color. 

Heated  in  a closed  tube,  the  sample  gives  off  bitumin- 
ous fumes  and  fumes  of  ammonia.  No  fossils  noted. 

Near  3000  ft. 

Sample  consists  of  about  3-4  dark  shale  and  1-4  light  gray 
sandstone.  Description: 

1.  Dark,  non-calcareous  indurated  shale.  Paint  bit- 
uminous fumes  and  strong  fumes  of  ammonia  given 
off  in  closed  tube.  Some  small  cylindric  bodies  about 
1-8  mm.  in  diameter.  2.  Very  light  gray,  non-cal- 
careous sandstone  of  fine  texture.  The  grains  are  angu- 
lar and  range  from  1-4  to  1-16  mm.  in  diameter. 

Strong  bituminous  fumes  and  deposits  of  oil  are 
shown  in  closed  tube,  with  slight  fumes  of  ammonia. 

No  fossils  present  3000  ft. 

Dirty,  yellowish  gray  sand,  mostly  from  1-4  to  1-8  mm.  in 
diameter.  On  heating  it  turns  dark  and  gives  weak 
fumes  of  sulphur  and  bitumen.  Some  fragments  of 
black  and  some  of  greenish  gray  shale  are  present.  A 
few  mica  scales  were  noted 3005  ft. 

Gray  sandstone  and  dark  shale.  The  sand  grains  are  mostly 

about  2 mm.  in  diameter  3006  ft. 

Dark  hard  shale  with  some  fine-grained  sandstone.  Heated 
in  closed  tube,  it  gives  bituminous  odor  and  strong 
ammonia  fumes.  No  fossils  noted.  Some  exceedingly 
fine  mica  present 3010  ft. 

Gray  sandstone  and  some  dark  shale.  Heated  in  closed  tube, 
gives  bituminous  odor,  sulphur  coat,  and  fumes  of 


ammonia.  The  sandstone  is  slightly  calcareous,  the 

sand  grains  are  mostly  1-4  mm.  in  diameter 3012  ft. 

Dark,  almost  black  shale,  and  fine-grained  sandstone 3019  ft 


pray  sandstone  and  some  dark  shale.  Heated  in  clased  tube, 
gives  bituminous  odor  and  ammonia  fumes.  The 
sandstone  if  fine  grained,  the  grains  being  about  Vs 
mm.  in  diameter,  and  they  lie  in  a matrix  of  black, 
probably  bituminous,  material.  All  sand  grains  are 
sharply  angular.  The  sandstone  is  slightly  micace- 
ous   3026  ft. 


The  Geology  of  Tarrant  County  113 

Hard  bluish-gray  shale  with  some  fine-grained  gray  sand- 
stone. Heated  in  closed  tube  gives  bituminous  and 
sulphur  odors  and  strong  ammonia  fumes.  In  thin 
section  the  sand  grains  are  seen  to  be  all  sharply 
angular  3030  ft. 

Gray  sandstone  and  some  black  shale.  Heated  in  closed  tube, 
gives  bituminous  odor  and  ammonia  fumes.  The  sand 
grains  mostly  measure  from  one-fourth  to  one-six- 
teenth mm.  in  diameter 3080  ft. 

Gray  sandstone  and  some  black  shale.  Heated  in  closed  tube 
gives  sulphur  odor  and  ammonia  fumes.  Grains  in 
sandstone  below  one-fourth  mm.  in  diameter 3095  ft. 

Bluish  black  shale.  Heated  in  closed  tube,  it  gives  bitu- 
minous odor  and  ammonia  fumes.  Shale  contains  a 
few  very  small  mica  scales  .3200  ft. 

Bluish  black  shale.  Heated  in  closed  tube,  gives  very  strong 

ammonia  fumes 3235  ft. 

Hard  bluish  gray  shale  and  gray  sandstone.  Heated  in  closed 
tube,  gives  bituminous  odor  and  strong  ammonia 
fumes.  The  sandstone  is  fine  grained,  hard,  slightly 
calcareous,  and  somewhat  micaceous;  quartz  grains 
angular  33  70  ft. 

Bluish-gray  shale  and  gray  sandstone.  The  sandstone  is 
very  fine-grained,  grains  measure  y8  mm.  or  less, 
with  a calcareous  matrix 3380  ft. 

Very  dark  shale  with  some  fine-grained  grayish  sandstone. 

Heated  in  closed  tube,  gives  bituminous  odor  and 
ammonia  fumes 3385  ft. 

Hard  gray  sandstone  and  hard  dark  shale 3565  ft. 

Hard,  dark  blue  shale  and  some  gray  shale.  Heated  in 
closed  tube,  gives  bituminous  odor  and  strong  am- 
monia fumes.  The  sand  grains  are  all  angular,  nearly 
all  below  % mm.  in  diameter  3575  ft. 

Hard,  grayish-blue  shale  and  a few  fragments  of  fine-grained 

gray  sandstone  3610  ft. 

Hard,  grayish-blue  shale.  Heated  in  closed  tube,  gives  bitu- 
minous odor  and  ammonia  fumes 3 615  fi. 

Hard,  bluish-black  shale  and  a little  gray  sandstone.  Heated 
in  closed  tube,  gives  bituminous  odor  and  strong 
ammonia  fumes.  In  thin  section  the  Shale  is  seen  to 
have  scattered  grains  of  quartz,  all  angular 3775  ft. 

Bluish  black  shale.  A few  buff  colored  fragments  of  lime- 
stone present.  Fumes  of  ammonia  and  sulphur  noted 
on  heating.  In  thin  sections  this  limestone  is  seen  to 
be  of  compact  texture  in  one  fragment.  Two  other 
sections  show  many  imbedded  organic  fragments, 
mostly  of  small  size.  Some  of  these  were  tubular, 
some  others  resembled  fragments  of  ostracod  shells.  .3800  ft. 


8— Tarrant 


114 


University  of  Texas  Bulletin 


Black  shale.  Heated  in  closed  tube  gives  very  strong 
ammonia  fumes  and  slight  sulphur  odor.  Ammodiscus 
noted  4060-4131  ft. 

Hard  black  shale  and  hard  gray  sandstone.  Heated  in 
closed  tube  gives  very  strong  ammonia  fumes.  Some 
rounded  quartz  grains  with  a diameter  of  one  half 
mm.  noted  4131-4141  ft. 

Hard  black  shale  and  some  hard  dark  gray  to  black  fine 
grained  sandstone.  Some  rounded  quartz  grains  about 
one  half  mm.  in  diameter  noted.  Heated  in  closed 
tube  give  strong  bituminous  odor  and  strong  ammonia 
fumes  4141-4147  ft. 

Hard  grayish  black  shale.  Some  rounded  quartz  grains 
present.  The  largest  of  these  measure  V2  mm.  in 
diameter.  Most  of  the  quartz  sand  is  about  one 
eight  mm.  and  less  in  diameter.  Heated  inclosed 
tube  gives  faint  bituminous  odor  and  faint  ammonia 
fumes  and  strong  odor  of  sulphur 4160-3214  ft. 

Hard  black  shale.  Some  quartz,  sand  grains  about  V2  mm. 
in  diameter  noted.  Heated  in  closed  tube  gives  strong 
ammonia  fumes  and  bituminous  odor 4295-4298  ft. 

Hard  grayish  black  sandy  shale.  Heated  in  closed  tube  gives 
strong  bituminous  odor  and  strong  ammonia 
fumes  . 4333-4339  ft. 

Grayish  white  sandstone  and  some  black  shale.  The  sand- 
stone consists  of  rounded  and  angular  quartz  grains. 

They  are  mostly  about  one-eighth  mm.  and  less  in 
diameter.  A few  are  one  quarter  mm.  in  di- 


ameter   - 434  2-4  352  ft. 

Hard  grayish  black  shale  and  gray  sandstone 4371-4380  ft. 


Black  hard  shale.  Some  slightly  calcareous  small  fragments 
are  present  in  fine  washed  material.  No  pyrite  nor 
fossils  were  seen.  In  closed  tube,  fumes  of  ammonia 
and  sulphur  were  noted.  Exast  depth  not  known. 


One  sample  said  to  be 4000+ ft. 

Another  larger  similar  sample  said  to  be. . . . 4600  ft. 


The  Geology  of  Tarrant  County 


115 


LOG  OF  WELL  NEAR  MANSFIELD,  TEXAS 

Feet 


Kind  of  Material 

From 

To 

Thickness  Formation 

Yellow  Clay 

0 

45 

45 

Sand 

45 

60 

15  Woodbine 

Water  (50-60) 

Black  shale 

60 

85 

25 

Sand 

85 

95 

10 

Water 

Dark  shale 

95 

115 

20 

Sand 

115 

125 

10 

Dark  shale 

125 

140 

15 

Sand 

140 

145 

5 

Light  shale 

145 

158 

13 

Brown  sand 

158 

164 

6 

Light  showing  oil  at  160 

Dark  shale 

164 

175 

11 

Water  sand 

175 

190 

15 

Light  shale 

190 

225 

35  Grayson 

Broken  lime 

225 

.255 

30 

Hard  lime 

255 

270 

15  Mainstreet 

Black  slate 

270 

292 

22 

Lime  stone 

292 

320 

28 

Dark  shale 

320 

340 

20  Pawpaw 

Broken  lime 

340 

350 

10  Weno 

Light  shale 

35,0 

375 

25 

Lime  stone 

375 

400 

25 

White  slate 

400 

410 

10  Denton,  Fort  Worth, 

Soft  lime 

410 

470 

60  Duck  Creek 

Brown  shale 

470 

500 

3 0 Kiamitia 

White  lime 

500 

575 

75  Fredricksburg 

Black  Slate 

575 

580 

5 

Lime 

,580 

600 

20 

Black  slate 

600 

612 

12 

Broken  lime 

612 

632 

20 

Black  slate 

632 

640 

8 

Hard  lime 

640 

648 

8 

Brown  shale 

648 

670 

22 

Sand 

670 

674 

4 

Water,  4 bailers  per  hour 

White  shale 

674 

688 

14 

116  University  of  Texas  Bulletin 


Feet 

Kind  of  Material  From  To  Thickness  Formation 


Red  shale 

688 

694 

6 

White  shale 

694 

740 

46  Paluxy 

Sand 

740 

806 

66 

Water 

Light  shale 

806 

814 

8 

Hard  lime 

814 

854 

40 

White  slate 

854 

862 

8 Glenrose 

Limestone 

862 

905 

43 

Dark  shale 

905 

912 

7 

Limestone 

912 

950 

38 

Sand 

950 

960 

10 

Water 

Light  shale 

960 

975 

15 

Broken  lime 

975 

1030 

55 

Hard  lime 

1030 

1040 

10 

Band 

1040 

1052 

12 

Artesian  water 

1042 

Hard  lime 

1052 

1095 

43 

Dark  slate 

1095 

1100 

5 

Broken  lime 

1100 

1156 

56 

Water 

Hard  line 

1156 

1165 

9 

Light  shale 

1165 

1215 

50 

Hole  full  of  water  at  1218 

Lime  and  sand 

1215 

1226 

11 

Blue  shale 

1226 

1258 

32 

Water  sand 

1258 

1270 

12 

Shale 

1270 

1275 

5 

Water  sand 

1275 

1288 

13 

White  shale 

1288 

1295 

' 7 

Water  sand 

1295 

1305 

10 

Slate  and  shell 

1305 

1340 

35 

Red  shale 

1340 

1359 

19 

Water  sand 

1359 

1400 

41 

Brown  shale 

1400 

1422 

22 

Red  rock 

1422 

1454 

32  Trinity  sand 

Water  sand 

1454 

1649 

15 

Red  rock 

1469 

1480 

11 

Water  sand 

1480 

1505 

25 

Showing  oil  at  1482 

Red  rock 

1505 

1517 

12 

Sand 

1517 

1530 

13 

Water  at  1522 


The  Geology  of  Tarrant  County 


1 


Kind  of  Material 

Feet 

From  To 

Thickness  Formation 

White  shale 

1530 

1532 

2 

White  sand 

1532 

1550 

18 

Strong  water  at  1533 

Red  shale 

1550 

1620 

70  Pennsylvanian 

Hard  sand 

1620 

1632 

12 

Red  shale 

1632 

1648 

16 

Dark  shale 

1648 

1665 

17 

Red  shale 

1665 

1670 

5 

Sand 

1670 

1678 

8 

White  slate 

1678 

1690 

12 

Dark  slate 

1690 

1722 

32 

Limy  sand,  hard 

1722 

1736 

14 

Dark  slate 

1736 

1795 

59 

Hard  lime 

1795 

1809 

14 

Dark  shale 

1809 

1840 

31 

Hard  lime 

1840 

1846 

6 

White  slate 

1846 

1875 

29 

Hard  sand 

1875 

1890 

15 

Red  shale 

1890 

1892 

2 

Hard  sand 

1892 

1909 

17 

Sandy  very  close,  but 
nice  showing  of  oil 
from  1895  to  1900 

Dark  shale 

1909 

1920 

11 

Lime  shell 

1920 

1926 

6 

Light  shale 

1926 

2015 

89 

Dark  shale 

2015 

2072 

57 

Sand  shell 

2072 

2075 

3 

Dark  shale 

2075 

2150 

75 

Lime  shell 

2150 

2155 

5 

Dark  shale 

2155 

2175 

20 

Limey  sand 

2175 

2190 

15 

Slate,  dark 

2190 

2205 

15 

INDEX 


Page 

Acanthoceras,  . 69 

swallovi 21,  83 

Aguilera  cumminsi 21,  82 

Aledo,  Texas 25,  36 

precise  levels 106 

Altitudes 101-6 

Anchura 66 

Animal  life 8 88-9 

Anomia 74 

Area 7.7.7.69’,  74 

gallieni g2 

Arcadia  Park,  Texas 83 

Arlington,  Texas 97 

precise  level 104 

Artesian  reservoirs 7.  . 97 

Astarte  acuminata 16 

Austin  Chalk 7.  7 . 78 

Avicula  leveretti 38 

Avondale.  Texas,  Precise  level  102 
Azle  road 28,  32,  35,  49 


Baculites 

Barbatia  micronema.  . . . . . ! 

simondsi 

Basement  sands 

Bear  Creek 

Benbrook,  Texas  ...77.7. 

precise  levels 7 

Bethel,  Texas,  precise  level 
Birds 


21,  69 
21,  82 
. . . 70 


25 

30 

27,  30,  49 

106 

105 


Birdville,  Texas 
Black  prairie.  . . 
Boese,  Emil .... 
Bottom  land 

plants 

Brick 

Brushy  knobs.  . 
Buda  limestone. 
Burleson,  Texas 
precise  level. 


75 

9 

57 

7 87 

89 

93-5 

10,  78,  80 

24 

73-5 

105 


Callianassa. 


Oelestite , 

O ± 

92 

Cenozoic  deposits.-. 

84 
7 A 

Cerithium 

bosquense.  . 

i 4: 

33 

51 

Duck  Creek.  . . 

interlineatum. 

82 

Chondrodonta  sp 

23 

90 

Cinulia 

.58, 

66* 

Li  O 

a q 

pelletti 

0 y 
74 

tarrantensis.  . 

.16, 

33 

0 

Olay 

Comanche  Peak  limestone 

.Comanchean  system 

Comptonia 

, 0 

27 

■25 

91 

Conglomerate,  Denton. 
Walnut 

Corbula 

22, 

33, 

66 

C-ottaldia.  . . . 

66 

Cotton  land 

7 

Crania 

22 

46 

c*i 

Cretaceous 

0 1 

g 

Comanchean 

25 

7 

82 

relation  to  cities 

Upper 

Crustacea.  . . . 

. 33 

82 

C-uesta  topography 8 

Cylindrites  formosus 

Cyphosoma  texanum.  . . . 

9, 

ll! 

.16, 

86 

33 

33 

Page 

volanum.  . ........21,  70,  73,  74 


Cyprimeria,  Kiamitia 23,  38 

texana 33 

Cytherea  leveretti 82 

Dallas,  Texas 76 

Dalliconcha  invaginata 16 

Declination,  magnetic 8 

Denison  beds 11 

Denton  marl... 58 

fossils 61 

section.  . 59 

Desert  varnish..... 82 

Desmoceras 39,  48 

brazoense.  . ...22,  51 

species  A 22,  51 

Dip  of  strata 10,  12,  100 

Dip  plain 11 

Diplopodia,  Duck  Creek 45,  51 

taffi 23,  28,  33 

Divides 87 

Drainage 12  86 

Duck  Creek  formation 39 

fossils 44,  50,  51 

section 42-3 

Eagleford  shale 10,  82 

Eastern  Cross  Timbers 10,  80,  88 

Edwards  limestone. 27 

Elephas  imperator ]...  84 

sp 84 

Ellenburger  limestone 97 

Enallaster 70 

bravoensis 21,  66,  70,  73,  74 

longisulcus 22 

Pawpaw 21,  69 

species  2 22,  51,  56,  58 

Texanus 23,  33,  66 

Engonoceras 66,  69 

aft.  piedernale 23 

Weno 22 

Epiaster  aguilerae 58 

elegans 15 

hemiasterinus 15 

Equus  francisii 84 

Escarpments 9 

Duck  Creek 49 

Goodland 13 

Weno ffi  13 

Excavations 85 

Exogyra ffi  70 

americana 19,  2.2  51,' 57,  58 

arietina 21,  70,  82 

columbella 82 

Grayson 21,  74 

plexa 16,  23,  28,  33,  38 

texana 23,  28,  33,  38 

weatherfordensis 33 


Fish  teeth 21,  51,  68,  69 

Flags 34,  59,  68 

Flickia 69 

Forest  Park 43,  49,  50,  118 

Fort  Worth  limestone.il,  16,  51,  85 

fossils 51  36-8 

section 52-6 

Fort  Worth,  Texas ....14,  85 

precise  levels 103,-6 

Fossils . 19-23 

Cenozoic.  84 

Denton 60—61 


120 


University  of  Texas  Bulletin 


Page 

Duck  Creek 39,  44-8,  50-51 

Eagleford 83 

Fort  Worth 51,  56-8 

Fredericksburg  division.  28,  30,  33 

Grayson 74 

Horizon  markers 21-3 

Kiamitia 38 

Mainstreet 7 0-7 1 

Nacreous,  Weno 61 

Pawpaw 68-69 

recurrent  horizons 18 

Weno 65,  66 

Woodbine 82 

Fredericksburg  division 26 

fossil  sequence 28,  30 

section.  . 29 

Fusus 51 


Page 

Inoceramus  comancheanus . . . 22,  51 


munsoni 22,  51 

Insects 89 

Iona,  Texas,  .precise  level 106 

Iron  ore,  in  Woodbine 81 

Ironstone,  in  Pawpaw 67 

Isocardia 33,  38 


Key  fossils 

Kiamitia  marl 

fossils 

section 

Kingena 

Denton  zone 

Duck  Creek  zones.  . . . 

19,  22, 

Mainstreet  zone 


20,  21-3 

38 

38 

35 

18,  21-22 

.19,  45 

'39;'  *4*4—5*,  51 
19,  21,  45,  70 


Gas 95-6 

Gervilliopsis  invaginata 

19,  22,  62,  64,  66 

Glenrose  limestone 12,  25,  98 

Glenwood  park 51 

Goniophorus 22,  46 

Goniopygus 33 

Goodland  limestone 13  27 

fo.ssils 33 

Grand  Prairie 11 

Gravel 12,  84,  91 

Graveyards,  Grayson 87 

Grayson  marl 72,  87 

fossils 74 

section 72-3 

Woodbine  contact 72-3 

Grazing  land 7 

Gryphea  corrugata 38,  48,  51 

Grayson 74 

marcoui 23,  27,  28,  33 

navia 23,  33,  38 

mucronata 21,  73,  74 

washitaensis 

21-3,  38,  51,  58,  60  61,  66 

Gypsum,  in  Woodbine 81 

Hamites 21,  22,  46,  48,  66,  69 

Comanchensis 22 

Duck  Creek 46,  48,  50 

fremonti 22,  51 

nokonis 22 

tanima 22 

Pawpaw 69 

tenawa 21 

Weno 66 

Handley,  Texas 75 

precise  level 104 

Haslet,  Texas 67 

Hawley,  J.  B 15 

Hemiaster  Oalvini.  . ..21,  66  73,  74 

elegans 22,  47,  51,  57,  58 

in  Fredericksburg 23,  28 

in  Pawpaw 21 

whitei 31,  51 

Heterodiadema  ornatum 15 

Hill,  R.  T 15,  25,  75 

Holaster  simplex * 22,  58 

low  phase 47 

tall  phase 47,  57 

Holectypus  limitis 21,  70 

planatus 23,  28,  33 

Homomya 21,  33,  38  66,  70 

Horizon,  of  fossil 17 

recurrent 18 

Horizon  markers 17 

Increment  in  thickness 68 


Lake  Worth  dam 28,  29 

Lamna. 27 

Lampasas  Cut  Plain 27 

Leiocidaris 21,  66,  70 

hemigranosus 61 

Lenticular  masses 76,  96 

Leptarbacia  argutus 15 

Life  zone,  Lower  Austral 7,  88 

semiarid 88 

Lignite,  in  Woodbine 81 

Lima 66,  74 

wacoensis 33,  51,  58,  61,  70 

Limestone  industries 89 

Limonite 18 

Lopha 70 

Lunatia  pedernalis 33 

species 51 

Magnetic  station 107 

Mainstreet  limestone 11  69 

fossils 70,  71 

Mammoth 12 

Mansfield 81 

well  log 115 

Marccu,  Jules 48 

Marine  Creek 37,  49 

Mary’s  Creek 30 

Mastodon 84 

Megatherium 84 

Metopaster  hortensae 21,  69 

Minerals 92 

Modiola  filisculpta 82 

Mortoniceras 69 

Nacreous  fossils,  Weno 61 

Natica  pedernales 23,  28 

tramitensis 82 

Nautilus  hilli 70 

in  Pawpaw 21 

texanus 58,  61,  66,  70 

Nerinea  aff.  pellucida 22 

Duck  Creek 51 

Fort  Worth 22 

Goodland 33 

Neritina 33 

Neritopsis  tramirensis 16 

Nodosaria  texana 21,  22,  66 

Noland’s  River 34,  61 

Nucula 66 

Oak  Cross  Timbers 12.  74 

Oil 81,  95-6 

Ophioglypha  texana 16,  58 

Ostrea  belliplicata 21,  83 

carica 21,  82 

carinata 19,  21, 

22,  51,  57,  58,  60,  61,  66,  70,  71 


The  Geology  of  Tarrant  County 


121 


Page 

marcoui 61,  66,  70 

quadfriplicata 21,  61,  66  TO 

soleniscus 21,  82 

sp.  aff.  johannae 33 

subovata 51,  58,  70 

Oxyrhina 66 

Pachymya 21,  58,  70 

Paluxy  sand 12,  25 

Water 98 

Parasmilia  austinensis . . . . 23,  28,  33 

Parker  County,  Texas,  precise 

levels 106 

Pawpaw  clay 67 

fossils 68-9 

section 68 

Peaks,  Walnut 32 

Woodbine 80 

Pecten  bellula 22,  47,  51,  58 

georgetownensis 22,  64 

irregularis 23,  28  33,  38 

Mainstreet  species 21,  70 

occidentalis 33 

roemeri f . . . 70 

subalpina 

21,  33,  38,  51,  58,  61,  66,  70,  74 

texanus 51,  61,  66,  70 

wrighti 22,  47,  51,  58,  70 

Pennsylvanian  system 25 

Pentagonaster  texensis 22,  66 

Pholadomya  in  Duck  Creek 51 

in  Kiamitia 23 

sancti-sabae 23,  28,  33 

shattucki 58,  70,  74 

Pinna 58 

in  Duck  Creek 22,  46,  51 

comancheanus 23,  33 

in  Kiamitia 38 

Pipe  clay 64 

Plants,  native 8,  89 

Pleurotomaria  austineneis 

22,  47,  51,  58 


Polytechnic,  Texas,  well  log....  107 

Precise  levels 102 

Preservation  of  fossils 18 

Prairie,  shortgrass 7 

Primrose  Texas,  precise  level..  104 

Protocardia 22,  61,  66,  74 

filosa 23,  28,  33 

texana 33,  38,  58 

vaughani 70 

Pseudomorph 18 

Pteria 58 

salinensis 82 

Ptychomya  ragsdalei 71 

Pyrite 18 

fossils,  Pawpaw 69 


Quadrula 84 

Quarry  limestone 21,  61 

in  C-ooke  County 64 

Railroads 14,  86 

Recent  deposits 84 

Recurrent  horizons 18 

Red  River  section..  45,  61,  37,  62,  64 

Remondia  acuminata 22,  66 

robbinsi 58 

River  bottom 87 

Restricted  zone 17 

Riverside,  Texas 67 

Roads 86 

Roanoke,  Texas 73 

Rostellaria  subfusiformis 33 

Round  Rock  Texas 34 

Rudistid,  at  Benbrook 27 


Page 

Saginaw,  Texas,  precise  level.  . . .102 


Salenia,  in  Duck  Creek 51 

in  Goodland 23,  30 

mexicana 23,  28,  33 

in  Pawpaw 21,  69 

in  Walnut 33 

S'alenid,  in  Grayson 74 

S'and 92 

in  Paluxy 26 

in  Trinity 26 

in  Walnut 32 

in  Woodbine 76 


Scapites,  in  Duck  Creek 

22,  39,  46,  51 


in  Pawpaw 21,  69 

in  Woodbine 82 

hilli 21 

wortiiensis 22 

Sehloenbac'nia.  . 21,  22,  47  66,  69,  70 

acutocarinata 23,  28,  33,  38 

belknapi 23,  3S 

elobiense 50 

inflata *. 4S 

sp.  aff.  belknapi 23 

sn.  J 51,  57 

rostrata 48 

triuodosa 39 

Serpula 58 

Shark  teeth 83 

Shawnee  Creek,  Grayson  County.  24 

S'huler,  E.  W 83 

Shumard,  B.  F 48 

S’oil 87 

Spondylus  cragini 70 

Starfish  zone 21,  69 

Stearnsia  robbinsi 16 

Stove  Foundry  Road 28,  30 

Sycamore  Creek 62,  67 

Svncline,  Pre-Cretaceous 97 


Taff,  J.  A *. 23 

Taff  and  Leverett 15 

Tapes 33,  58,  66,  74 

Tarrant  County  agricultural  di- 
visions  7 

altitudes 9,  101-6 

drainage 12,  36 

geological  formations  of 24 

location 8 

map 14-15 

population 7 

topographic  divisions 9 

type  localities 15 

Tarrant,  Texas 75,  80 

Terraces 47 

in  Duck  Creek 48 

in  Weno 62 

Timbered  land 7,  89 

Travilla,  J.  C 15 

Trichotropis  shumardi 16,  33 

Trigonarca  siouxensis 82 

Trigonia 

22,  33,  38,  51,  58,  61,  66,  70,  74 

Trinity  division 25 

water 98 

Trinity  River 12-13 

headwaters 13 

valley 14,  87 

Trochosmilia,  in  Fort  Worth.  ...  58 

in  Pawpaw 21,  66 

texana 23  28,  32 

Trochus 66 

Turbo 33,  51,  66 

Turrilites 69,  70 

brazoensis 21,  70 

in  Duck  Creek 45,  51,  69 


122 


University  of  Texas  Bulletin 


„ Page 

m Grayson 74 

in  Pawpaw 69 

species  A 21 

Turritella 22,  33,  51,  66,  74 

coalvillensis 82 

marnochi 58 

renauxiana 82 

seriaiim-igranulosa 33,  58 

Tylostoma  chihuahuense 33 

tumidum 33 

Type  localities,  in  Tarrant 
County 15 

Udden,  J.  A 1.10 

Upland  formations 13,  14,  87 

plants 89 

soils 87 

Venericardia 22 

Virgile,  Texas,  precise  level....  104 

Vola  bellula 16 

Walnut  formation 12,  13  32 

fossils • 33 

Washita  division 33 

Water  supply 97 

Wells 99 

fossils  in  samples 20 

at  Mansfield 115 


at  Polytechnic 25,  99,  107 

samples  from  Polytechnic  well  110 

Tucker’s  Hill 25 

Weno  formation 61 

at  Red  River 61,  64 

fossils 65-6 

on  S’ycamore  Creek 62 

section 65 

Western  Cross  Timbers 12 

White  Rock  Cliff 10,  83 

Wood,  fossil 81 

Woodbine  formation.  . 10,  13,  24,  74 

cross-bedding -...10,  80 

dip 76,  80 

Eagleford  contact 83 

faulting 81 

flora.  . 89 

fossils 76,  82 

Grayson  contact 72-3 

lenticular  masses 10,  76,  96 

outliers 10 

section 76 

water  reservoir 98 

Zone  of  abundance 17 

of  fossils 17 

recurrent 18 


EXPLANATION  OF  MAP  SHOWING  GEOLOGICAL  HORIZONS 
AND  LOCALITIES  IN  THE  FOREST  PARK-TEXAS 
CHRISTIAN  UNIVERSITY  AREA. 

In  the  accompanying  large  scale  map  of  this  area,  four  square 
miles  in  extent,  there  are  shown  a few  typical  and  easily  recog- 
ized  horizons  and  a few  unusually  good  collecting  localities. 
This  region  is  reached  by  a short  street  car  ride  from  Fort  Worth 
(Forest  Park  car),  and  is  an  excellent  one  in  which  to  make 
studies  of  many  of  the  formations  discussed  in  this  paper.  All 
the  Comanchean  formations  from  the  Goodland  to  the  Main- 
street  are  exposed  in  this  area.  The  Goodland  limestone  (Fred- 
ericksburg) is  exposed  in  the  northwest  corner  of  this  area,  but 
for  only  a few  vertical  feet  at  the  top  of  the  formation.  The 
Lake  Worth  and  Benbrook  sections  are  much  better  for  this  for- 
mation. This  small  area  is  especially  rich  in  fossiliferous  ex- 
posures of  the  Duck  Creek  and  Fort  Worth  formations.  For 
complete  succession  lists  of  the  fossils  of  the  various  formations, 
see  the  text  for  the  formations  in  question. 

ABBREVIATIONS'  USED  ON  THE  MAP 

* Good  fossil  locality. 

. .T.  . Turrilites  brazoensis:  Mainstreet  limestone,  middle.1 

P Pyrite  fossils,  Area,  Turrilites:  Pawpaw  clay,  base. 

N Nodosaria  texana:  Weno  limestone,  middle. 

E Exogyra  americana:  Fort  Worth  limestone,  middle. 

S Schloenbachia  small  sp.:  Fort  Worth  limestone,  base. 

Hoi  Holaster  simplex:  Duck  Creek  marl,  top. 

. . K.  . Main  Kingena  zone:  Duck  Creek  marl,  top.1 

..H..  Hamites  zone:  Duck  Creek  limestone,  base.  Just  above 

and  parallel  to  this  zone  is  the  striking  Desmoceras  hori- 
zon of  the  Duck  Creek  limestone.1 

D Desmoceras  horizon:  Duck  Creek  limestone,  base. 

G Gryphea  navia:  Kiamitia  marl,  thruout. 


xThe  three  continuous  dotted  lines  on  the  opposite  map  lettered 
H,  K and  T,  indicate  the  outcrop  of  the  Hamites  zone,  the  Main 
Kingena  zone  and  the  Turrilites  brazoensis  zone  respectively,  as 
mentioned  in  the  above  list  of  abbreviations.  The  other  letters 
refer  to  good  localities  for  the  corresponding  fossils,  as  listed  above. 


IbO  l 


C 

2 

c 


> 

< 

E- 


32“  42 


University  of  Texas  Bulletin  No.  1931 


a • 
o ,a 

? " 

si 


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Plate  2.  Fig.  1.  Airplane  view  of  top  of  Goodland  limestone,  Benbrook, 
Texas.  (Locality  described  by  Taff.) 


Plate  2.  Fig.  2.  GoodJpnd  Hmestone.  '’"eve  Foundry  Poa'U  4 
miles  west  of  Fort  Worth.  The  base  of  the  telephone 
pole  is  the  Upper  Salenia  horizon. 


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Plate  3.  Fig.  1.  Top  of  Goodland  (Fredericksburg)  limestone, 
looking  east  from  near  Benbrook. 


Plate  3.  Fig.  2.  Terrace  in  the  Fredericksburg  division.  The 
top  terrace  is  the  top  of  the  Goodland. 


Plate  3.  Fig.  3.  Terraces  in  the  basal  Washita  Division.  The 
bottom  terrace  is  the  top  of  the  Goodland  limestone, 
and  the  top  two  are  the  Duck  Creek  limestone  and 
marl. 


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University  of  Texas  Bulletin  No.  1931 


Plate  4.  Fig.  1.  Base  of  Fort  Worth  limestone,  which  underlies 
the  business  section  of  the  City  of  Fort  Worth.  On 
Main  Street,  the  base  of  the  limestone  is  about  30 
feet  underground.  The  limestone  is  underlain  by 
the  less  resistant  Duck  Creek  marl. 


Plate  4.  Fig.  2.  Gate  posts  and  flower  beds  in  Forest  Park,  built 
of  the  large  ammonite,  Desmoceras  brazoense. 


,r ' V. 


& 


i 


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Plate  5.  Fig.  1.  The  large  ammonite,  Schloenbachia  sp.  J.,  which 
characterizes  the  Fort  Worth  limestone. 


Plate  5.  Fig.  2.  Illustration  of  the  terms  “cast”  (left)  and  “mold” 
(right). 


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University  of  Texas  Bulletin  No.  193J 


Plate  6.  Fort  Worth  limestone,  in  excavation  at  northwest  corner 
of  8th  and  Houston  sts.,  Fort  Worth.  Excavations  for 
buildings  in  the  main  business  district  pass  into  or 
entirely  through  the  Fort  Worth  limestone. 


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HJN4  1973 


University  of  Texas  Bulletin 

No.  1932:  June  5,  1919 

The  Geology  and  Mineral 
Resources  of  Bexar  County 


By 

E.  H.  SEIXARDS 


BUREAU  or  ECONOMIC  SEOIOOY  SND  TECHNOLOGY 
t „ TT_  DIVISION  OF  ECONOMIC  'GEOLOGY 
J.  A.  UDDEN,  Director  of  the  Bureau  and  Head  of  the  Division 


PUBVPS”E"AY  THE  UN1VERSITY  six  times  a month,  and  entered  as 

SECOND-CLASS  MATTER  AT  THE  POSTOFFICE  AT  AUSTIN.  TEXAS. 
UNDER  THE  ACT  OF  AUGUST  24,  1912 


geology 


The  benefits  of  education  and  of 
useful  knowledge,  generally  diffused 
through  a community,  are  essential 
to  the  preservation  of  a free  govern- 
ment. 

Sam  Houston 


Cultivated  mind  is  the  guardian 
genius  of  democracy.  . . It  is  the 

only  dictator  that  freemen  acknowl- 
edge and  the  only  security  that  free- 
men desire. 


Mirabeau  B.  Lamar 


2.  x,  /W£*  o ) ^ Y 3 


CONTENTS 


r * 

fN.-'f  _3 


r 


Introduction  

Early  settlements 

Acknowledgments 

Location  with  respect  to  major  physiographic  divisions 

Topography  and  drainage 

Climate  and  rainfall  

Balcones  Escarpment  

Minor  physiographic  divisions 

The  Glenrose  hills 

The  Edwards  flint  hills 

The  Del  Rio  plain 

The  Austin  hills  

The  Taylor-Navarro  plain 

The  Midway- Wilcox  hills 

The  Carrizo  sand  hills 

Stream  terrace  plains 

Stratigraphic  geology  

The  Pre-Cretaceous  sediments 

Table  of  geologic  formations 

The  Mesozoic 

Comanchean  Cretaceous  

Trinity 

Travis  Peak  formation  

Glenrose  formation 

Fredericksburg 

Comanche  Peak  formation  

Edwards  formation  

Washita 

Georgetown  formation 

Del  Rio  formation 

Buda  formation  

Upper  Cretaceous 

Eagle  Ford  formation 

Austin  formation 

Taylor  formation  

Navarro  formation 

The  Cretaceous-Tertiary  contact 

The  Cenozoic 

Eocene  

Midway  formation 

Wilcox  formation 

Carrizo  formation 

Pleistocene 

Uvalde  formation 

Leona  formation  


7 

7 

8 

TO 

12 

13 

13 

14 

14 

15 

16 

16 

17 

18 

18 

18 

19 

19 

20 

21 

21 

21 

23 

24 

25 

27 

28 

31 

34 

34 

36 

44 

49 

53 

54 

54 

54 

57 

63 

64 

65 

69 


Contents 


Late  Pleistocene  Alluvial  deposits 72 

Cave  deposits 73 

Recent 74 

Calcareous  concretions  75 

Structural  geology 77 

Location  of  principal  faults 77 

Structurally  high  areas  82 

The  Culebra  structure 83 

The  San  Antonio  structure 84 

The  Alta  Vista  structure 85 

The  Geological  Map 86 

Index  to  levels  on  the  Del  Rio  formation 87 

Notes  on  exposures  seen  on  the  public  roads,  including 
Blanco,  Bulverde,  Nacogdoches,  Austin,  St.  Hedwig, 
Pleasanton,  Somerset,  Pearsall,  Castroville,  Potranca 
Culebra,  Bandera,  Babcock  and  Fredericksburg 

roads. 90 

Economic  Geology  97 

Artesian  and  other  underground  waters 97 

Principles  of  artesian  wells  and  ground-water  ac- 
cumulation   98 

Water  of  the  Glenrose-Travis  Peak  formations 100 

Water  of  the  Georgetown-Edwards  limestones 101. 

Areas  of  artesian  flow  101 

Water  of  the  Del  Rio  and  Buda  formations 103 

Water  of  the  Eagleford  and  Austin  formations 104 

Water  of  the  Taylor  and  Navarro  formations 104 

Water  of  the  Tertiary  formations 104 

Springs  104 

Warm  sulphur  water  in  the  Comanchean  limestones. . . .105 
Source  of  hydrogen  sulphide  in  underground  waters. . .106 

Cement  108 

Clay  112 

Building  brick  112 

Fuller’s  earth 114 

Bentonite  115 

Concrete  116 

Greensand  117 

Lignite  118 

Limestone  119 

Lime  120 

Building  stone  121 

Petroleum  and  Natural  gas 121 

The  Alta  Vista  oil  field  122 

The  Mission  oil  field 123 

The  Gas  Ridge  oil  and  gas  field 123 

The  Somerset  oil  field 124 


Contents 


The  South  Medina  oil  field 125 

Relation  of  the  Bexar  County  oil  fields  to  structure 125 

Quality  of  the  Bexar  County  oil 127 

General  considerations  127 

Road  materials . 128 

Well  records  129 

Wells  entering  the  Pre-Cretaceous  formations 129 

Wells  terminating  in  the  Comanchean  formations 135 

Tabulated  records  136 

Logs  and  other  data  supplementary  to  the  tab- 
ulated records  143 

Wells  terminating  in  the  Upper  Cretaceous 171 

Index  199 


ILLUSTRATIONS. 


Fig.  1. 

Fig.  2. 

Fig.  3. 
Fig.  4. 

Fig  5. 

Fig  6. 


Figures. 


Page 


Sketch  map  to  show  the  location  of  Bexar  County 
with  respect  to  the  major  physiographic  provinces 

of  Texas 11 

Sketch  map  to  show  the  minor  physiographic  prov- 
inces in  Bexar  County  . 15 

Table  of  geologic  formations  and  columnar  section.  . 20 
Graphic  representation  of  logs  of  wells  arranged 
in  order  from  northwest  to  southeast 78 


Schematic  representation  of  structure  on  an  approx- 
imately north-south  line  through  Bexar  County. ...  79 
Sketch  map  indicating  the  location  of  brick,  cement 
and  fullers  earth  plants,  lime  kilns,  lignite  mine, 
oil  and  gas  fields,  and  areas  of  flowing  artesian 
water  98 


Plate. 

PI.  1.  Pisolitic  gravel  in  the  Pleistocene  as  seen  in  pit  ex- 
cavated for  gravel  road  material  near  the  Mission 
Loop  Road  south  of  San  Antonio 72 


Map. 

Geologic  and  structural  map  of  Bexar  County . . Inside  back  cover 


GEOLOGY  AND  MINERAL  RESOURCES  OF 
BEXAR  COUNTY* 


BY  E.  H.  SELLARDS 

Bexar  Coujity  is  located  in  south-central  Texas,  about  125 
miles  from  the  Gulf  Coast,  and  approximately  an  equal  distance 
from  the  Mexican  border.  The  adjoining  counties  are  Kendall 
and  Comal  on  the  north,  Guadalupe  and  Wilson  on  the  east, 
Atascosa  on  the  south,  and  Medina  and  Bandera  on  the  west. 
San  Antonio,  the  county-seat,  is  one  of  the  large  cities  of  the 
southwest  part  of  the  United  States.  The  area  of  Bexar  County 
is  estimated  at  1,268  square  miles.  The  population,  according  to 
the  latest  census,  that  of  1913-1914,  was  119,676. 

EARLY  SETTLEMENTS 

In  1718  the  Spanish  established  the  mission  of  San  Antonio 
de  Valero  and  the  Villa  de  Bexar  near  the  headwaters  of  the  San 
Antonio  River  and  on  the  site  of  the  present  city  of  San  Antonio. 
The  principal  natural  advantage  inducing  settlement  at  this 
place  was  the  existence  of  large  springs  which  emerge  at  the 
head  of  the  San  Antonio  River  a few  miles  farther  inland.  The 
location  for  this  setllement  is  said  to  have  been  pointed  out  to 
the  Spaniards  by  the  Frenchman,  Saint  Denis,  as  a suitable 
place  for  a city  “in  the  most  pleasant  place”  in  the  province  of 
Texas.!  Subsequently,  between  the  years  1718  and  1731,  there 
was  built  up  by  the  Spanish,  the  several  missions  of  which  the 
ruins  still  remain.  Of  these,  the  mission  of  San  Antonio  de 
Valero,  already  noted,  and  Conception  Mission  are  within  the 
limits  of  the  present  city  of  San  Antonio.  The  others  are  farther 
south,  but  all  are  within  the  valley  of  the  San  Antonio  River, 
where  water  from  the  springs  was  available  and  was  used  in 
irrigation.  The  presence  of  these  springs,  giving  rise  to  a per- 
manent flowing  stream  in  a region  otherwise  lacking  in  surface 
water  supplies,  determined  the  original  location  of  the  city  of 
San  Antonio. 

fClark,  Robert  Carlton.  The  Beginnings  of  Texas.  Univ.  of  Texas 
Bull.  No.  98,  p.  87,  1907. 

♦Issued  March,  1920. 


8 


University  of  Texas  Bulletin 


Settlement  by  citizens  of  the  United  States  began  in  Bexar 
County  while  Texas  was  still  a Spanish  province,  although  not 
until  1820  was  official  permission  secured  to  establish  an  Ameri- 
can colony.  Immigration  from  the  United  States  continued  and 
at  the  time  of  the  declaration  of  independence  of  Texas,  a con- 
siderable colony  had  been  established.  The  historic  associations 
of  the  city,  especially  those  connected  with  the  struggle  for  in- 
dependence from  Mexico,  center  around  the  Alamo,  built  orig- 
inally as  the  chapel  of  the  Mission  of  San  Antonio  de  Valero, 
where  in  1836  Colonel  Travis  and  his  small  band  of  182  follow- 
ers made  their  famous  although  unsuccessful  stand  against  the 
army  of  Santa  Anna. 

Since  the  acquisition  of  Texas  by  the  United  States,  the 
military  control  of  the  southwest  has  in  a measure  centered  in 
San  Antonio,  and  at  the  present  time  the  county  is  notable  for 
the  number  of  army  camps  and  large  military  reservation  that 
it  contains.  Fort  Sam  Houston,  near  the  eastern  limits  of  San 
Antonio,  has  for  many  years  been  the  headquarters  for  the 
Southern  Military  Department.  The  Leon  Springs  military 
reservation  is  located  in  the  northern  part  of  the  county.  South 
of  Leon  Springs  is  the  Camp  Bullis  reservation,  now  under  lease 
by  the  Government.  Adjoining  Fort  Sam  Houston  on  the  east, 
and  partly  within  the  city  limits,  is  a large  army  training  camp 
named  in  honor  of  Colonel  W.  B.  Travis.  Camp  Stanley,  a 
cavalry  camp,  is  located  in  the  Leon  Springs  reservation.  Kelly 
field  No.  1 and  Kelly  Field  No.  2,  both  aviation  camps,  are  lo- 
cated on  the  terrace  plain  about  six  miles  southwest  of  the  center 
of  the  city.  Brooks  Field,  another  aviation  camp,  is  about  eight 
miles  south  of  San  Antonio.  Camp  John  Wise  Balloon  School 
is  located  just  north  of  the  city  limits. 

ACKNOWLEDGMENTS 

An  investigation  of  the  geology  of  Bexar  County  was  begun 
for  the  Bureau  of  Economic  Geology  by  Mr.  C.  L.  Baker,  in 
1917.  The  field  notes  made  by  Mr.  Baker  at  that  time  have  been 
available  and  have  proved  of  much  assistance  in  the  subsequent 
field  work  in  this  county  and  in  the  preparation  of  this  report. 


Geology  and  Mineral  Resources  of  Bexar  County  9 

Dr.  J.  A.  Udden,  has  also  made  notes  at  various  times  on  this 
county,  both  on  surface  exposures  and  on  cuttings  from  deep 
wells.  These  notes  likewise  have  been  made  available  and  have 
been  used  in  this  report.  In  1911  and  again  in  1918,  Dr.  L.  W. 
Stephenson  of  the  U.  S.  Geological  Survey  visited  and  made 
notes  on  the  geology  of  Bexar  County.  A part  of  the  data  in 
Dr.  Stephenson’s  notes  was  incorporated  by  him  in  a paper  on 
“The  Camps  Around  San  Antonio”,  published  on  the  reverse 
side  of  the  topographic  map  of  the  San  Antonio  quadrangle, 
edition  of  1919.  The  unpublished  notes  by  Dr.  Stephenson  have 
very  generously  been  placed  at  the  disposal  of  the  Bureau  of 
Economic  Geology  by  the  Director  of  the  United  States  Geo- 
logical Survey,  and  have  added  very  materially  to  the  data 
on  this  county.  From  Mr.  Alexander  Deussen  many  additional 
data  have  been  secured,  including  well  records  collected  by  him 
in  connection  with  a report  on  the  water  supply  of  Central  Texas 
for  the  U.  S.  Geological  Survey,  as  well  as  other  data  personally 
collected  by  himself.  Brief  reports  on  oil  discoveries  in  Bexar 
County,  made  for  the  Bureau  of  Economic  Geology  by  Mr.  E.  L. 
Porch,  Jr.,  have  been  available  and  have  supplied  data  utilized 
in  this  report.  To  Mr.  R.  M.  Madison  is  due  credit  for  many 
data  on  wells.  To  the  Chamber  of  Commerce  of  San  Antonio, 
to  well  drillers,  and  oil-  and  mineral-producing  companies  as 
well  as  to  many  other  individuals,  the  writer  is  under  obligations 
for  courtesies  and  for  data  that  have  been  contributed. 

The  base  maps  which  have  been  available  in  this  county  in- 
clude, first,  a topographic  map  of  the  San  Antonio  quadrangle, 
by  the  United  States  Geological  Survey.  This  quadrangle  covers 
approximately  one-half  of  the  county.  From  the  County  En- 
gineer of  Bexar  County,  Mr.  A.  C.  Pancoast,  was  obtained  a very 
carefully  made  road  map  of  the  county  which  has  been  of  much 
service.  In  addition,  maps  of  the  military  reservations  were 
available  in  the  offices  of  the  War  Department.  The  soil  survey 
map  of  the  San  Antonio  area  made  by  the  United  States  Bureau 
of  Soils  was  likewise  consulted. 

The  published  literature  relating  directly  or  indirectly  to 
Bexar  County,  although  not  extensive,  includes  a number  of 
papers  that  should  be  specially  mentioned.  The  following  list 


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University  of  Texas  Bulletin 


contains  the  more  important  papers  relating  to  this  county,  ar- 
ranged chronologically : 

A Partial  Report  on  the  Geology  of  Western  Texas,  consisting  of  a 
general  Geological  Report  and  a Journal  of  Geological  Observations 
along  the  Routes  traveled  by  the  Expedition  between  Indianaola, 
Texas,  and  the  Valley  of  the  Nimbres,  New  Mexico,  during  the  years 
1855  and  1856;  with  an  Appendix  giving  a detailed  report  on  the 
Geology  of  Grayson  County.  By  Prof.  Geo.  G.  Shumard,  Assistant 
State  Geologist  of  Texas.  Introduction  by  H.  P.  Bee,  Commis- 
sioner of  Insurance,  Statistics  and  History.  Austin,  1886. 

Report  on  the  Brown  Coal  and  Lignite  of  Texas,  by  Edwin  T. 

Dumble.  Second  Annual  Report,  Texas  Geological  Survey,  1892. 
Geology  of  the  Edwards  Plateau  and  Rio  Grande  Plain  adjacent  to 
Austin  and  San  Antonio,  Texas,  with  reference  to  the  occurence 
of  Artesian  waters,  by  Robert  T.  Hill  and  T.  W.  Vaughan.*  U.  S. 

’ Geological  Survey,  18th  Ann.  Rpt.,  Pt.  II,  pp.  193-321,  1898. 
Geography  and  Geology  of  the  Black  and  Grand  Prairies,  Texas, 
with  detailed  descriptions  of  the  Cretaceous  formations  and  spe- 
cial reference  to  artesian  waters,  by  R.  T.  Hill.  U.  S.  Geol.  Surv., 
21st  Ann.  Rpt.,  Pt.  VII,  pp.  666,  80  figs.,  1901. 

Soil  Survey  of  the  San  Antonio  Area,  Texas,  by  Thomas  A.  Caine  and 
W.  S.  Lyman.  U.  S.  Dept.  Agric.,  Bureau  of  Soils,  1904. 
Underground  Waters  of  the  Coastal  Plain  of  Texas,  by  Thos.  U. 

Taylor.  U.  S.  Geol.  Surv.,  Water  Supply  Paper  No.  190,  1907. 

The  Geology  of  the  Artesian  Water  Supply  of  the  San  Antonio  Area, 
by  A.  H.  Muir.  San  Antonio,  1911. 

Geology  and  Underground  Waters  of  the  Southeastern  part  of  the 
Texas  Coastal  Plain,  by  Alexander  Deussen.  U.  S.  Geol.  Surv., 
Water  Supply  Paper  No.  335,  1914. 

The  Mineral  Resources  of  Texas,  by  Win.  B.  Phillips.  Bulletin  of 
the  University  of  Texas,  No.  365,  1914. 

The  Lower  Eocene  Floras  of  Southeastern  North  America,  by  E.  W. 

Berry.  U.  S.  Geol.  Surv.,  Prof.  Paper  No.  91,  1916. 

Review  of  the  Geology  of  Texas,  by  J.  A.  Udden,  C.  L.  Baker,  and 
Emil  Bose.  Bull.  Univ.  Texas,  No.  44,  1916. 

LOCATION  WITH  RESPECT  TO  MAJOR  PHYSIOGRAPHIC 
PROVINCES 

Two  of  the  large  physiographic  provinces  of  the  United  States, 
namely  the  Gulf  Coastal  Plain  and  the  Great  Plains,  extend 
into  Bexar  County.  The  Gulf  Coastal  Plain,  in  which  the  greater 
part  of  the  county  lies,  reaches  from  Central  America,  bordering 
the  Gulf  of  Mexico,  to  the  Atlantic  Ocean,  there  merging  with 
the  Atlantic  Coastal  Plain.  The  Great  Plains,  including  several 


Geology  and  Mineral  Resources  of  Bexar  County  11 

sub-divisions,  extend  from  Mexico  to  the  Arctic  Ocean.  In  cen- 
tral and  southern  Texas  the  line  dividing  the  Great  Plains  and 
the  Gulf  Coastal  Plain  is  a pronounced  southeast  to  south  facing 
escarpment  produced  by  faults  and  dips,  and  known  as  the  Bal- 
cones  Escarpment.  This  escarpment,  coming  into  the  state  near 
Del  Rio  on  the  Rio  Grande  River,  continues  east  to  Medina 
County  and  there  turns  to  the  northeast,  passing  through  Bexar 
County  in  a direction  approximating  60  degrees  east  of  north. 
Approximately  seven-eighths  of  the  county  lies  in  the  Gulf 
Coastal  Plain  southeast  of  the  escarpment,  while  the  remaining 
one-eighth,  or  about  150  square  miles,  lies  to  the  northwest  in 
the  margin  of  the  highlands  known  as  the  Edwards  Plateau, 
which  is  the  southernmost  division  in  Texas  of  the  Great  Plains. 
The  location  of  the  county  in  the  State,  and  with  respect  to 
these  major  physiographic  divisions,  is  indicated  on  the  ac- 
companying sketch  map  (fig.  1). 


Fig.  1. — Sketch  map  to  show  the  location  of  Bexar  County  with 
respect  to  the  major  physiographic  provinces  of  Texas.  The  shaded 
area  indicates  the  location  of  Bexar  County. 


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University  of  Texas  Bulletin 


TOPOGRAPHY  AND  DRAINAGE 

The  topographic  and  physiographic  divisions  in  Bexar  County 
are  determined  very  largely  by  the  geologic  structure.  The 
formations  dip  in  general,  and  with  some  variations,  to  the  south- 
east. This  also  is  the  direction  of  the  average  maximum  surface 
slope,  but  as  the  rate  of  dip  of  the  formations  is  more  rapid  than 
the  surface  slope,  it  follows  that  in  passing  to  the  southeast 
younger  formations  come  successively  into  the . section.  Each 
formation  develops  in  the  line  of  its  outcrop  a more  or  less  well 
defined  surface  topography  or  topographic  expression  which  is 
often  very  characteristic  for  that  particular  formation.  The 
formations  containing  much  hard  rock  resist  decay  and  stand 
out  as  hills,  often  forming  northwest-facing  escarpments  or 
“cuestas”.  The  softer  and  less  resistant  formations,  on  the 
other  hand,  produce  either  valleys  or  plains.  The  strike  of  the 
formations,  as  already  indicated,  is  in  general  northeast-south- 
west. Accordingly,  the  topographic  areas  developed  from  these 
formations  trend  in  a northeast-southwest  direction  across  the 
county.  In  addition  to  topographic  divisions  dependent  upon 
the  surface  outcropping  of  the  formations,  there  is  in  this  county 
a large  development  of  flood  plain  stream  deposits.  These 
plains,  some  of  which  are  extensive  in  area,  cut  across  and  cover 
over  the  successive  formations,  concealing  the  surface  features 
that  otherwise  would  have  characterized  the  outcropping  of  the 
underlying  rocks.  The  formations  to  which  it  is  necessary  to 
refer  in  this  discussion  of  topography  are  more  fully  described 
in  the  section  on  Geology.  They  include  formations  of  the  Cre- 
taceous and  Cenozoic  systems. 

The  surface  drainage  in  Bexar  County  is  to  the  south  or  south- 
east in  the  direction  of  average  surface  slope.  The  maximum 
elevation  is  at  the  northern  part  of  the  county  and  approximates 
or  exceeds  1500  feet  above  sea  level,  while  near  the  southern 
boundary  of  the  county  the  elevation  is  500  or  600  feet  above 
sea  level.  The  principal  stream  is  the  San  Antonio  Riverf  which 
heads  in  this  county  and  flows  southeast  to  the  Gulf  at  San 
Antonio  Bay.  Among  smaller  streams  in  the  county,  all  of  which 
flow  directly  or  indirectly  into  the  San  Antonio  River,  are  the 


Geology  and  Mineral  Resources  of  Bexar  County  13 

following : Medina,  Medio,  Leon,  Helotes,  Salado,  and  Calaveras. 
Rio  Cibolo  forms  a part  of  the  northern  and  eastern  boundaries 
of  the  county.  With  the  exception  of  the  San  Antonio  River 
and  Salado  Creek,  which  are  supplied  by  large  springs,  all  of 
these  streams  are  in  at  least  a part  of  their  course  intermittent, 
flowing  for  only  a short  time  following  rains. 

CLIMATE  AND  RAINFALL 

Bexar  County  is  intermediate  in  location  between  the  arid 
southwest  and  the  much  more  moist  climate  of  the  Coastal 
Plains.  The  following  data  on  temperature  and  rainfall  are 
taken  from  reports  of  the  United  States  Weather  Bureau,  and 
are  based  on  the  records  from  1885  to  1903.  The  annual  mean 
temperature  at  San  Antonio  as  obtained  from  these  records  is 
69  degrees  F.  The  mean  for  the  four  seasons  of  the  year  is  as 
follows:  winter,  54;  spring,  69;  summer,  82;  fall,  70.  The 
maximum  summer  heat  recorded  within  this  period  is  106 
degrees  F.  The  minimum  winter  temperature  recorded  is  4 
degrees  F. 

The  annual  mean  rainfall  for  the  same  interval  was  28.4 
inches.  This  is  distributed  throughout  the  year  on  an  average  as 
follows:  January,  1.7;  February,  1.9;  March,  1.8,  April,  2.9; 
May  3.0;  June,  2.7;  July  2.6;  August,  3.1;  September,  3.4; 
October,  1.8;  November,  1.8;  December,  1.7. 

BALCONES  ESCARPMENT 

A prominent  topographic  feature  in  this  county,  already  re- 
ferred to,  is  the  Balcones  Escarpment  which  passes  through  the 
county  in  a northeast-southwest  direction.  To  the  northwest  of 
this  escarpment,  the  country  is  high,  and  in  this  county  hilly; 
but  to  the  southeast  the  land,  although  in  places  hilly;  is  on  the 
average  much  lower  in  elevation,  including  also  a larger  amount 
of  level  land  and  flood  plains.  This  escarpment  enters  the  county 
at  the  west  boundary  a few  miles  north  of  the  Culebra  Road,  and 
leaves  at  the  big  bend  of  the  Cibolo  in  the  northeast  corner  of 
the  county.  The  hills  of  this  escarpment  are  entered  on  the 
Bandera  Road  18  miles  from  San  Antonio;  on  the  Fredericks- 


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University  of  Texas  Bulletin 


burg  Road,  16  miles;  on  tbe  Blanco  Road,  18  miles;  and  on  tlie 
Bulverde  Road,  about  21  miles  from  San  Antonio. 

This  escarpment  indicates  the  location  of  the  first  largo  faults 
and  dips  of  the  Balcones  fault  zone.  In  the  western  part  of 
Bexar  County  the  escarpment  is  abrupt.  In  the  eastern  part  of 
the  county  on  the  other  hand  the  escarpment  is  not  so  pro- 
nounced, the  Edwards  Plateau  rising  more  gradually  from  the 
lowlands.  These  differences  in  topography  which  indicate  dif- 
ferences in  the  amount  of  faulting  are  more  fully  discussed  in 
the  section  on  structural  geology. 

MINOR  PHYSIOGRAPHIC  DIVISIONS 

Several  well  characterized  minor  physiographic  divisions  are 
recognized  in  this  county.  These  areas  for  the  most  part  form 
belts  which  trend  with  the  formations  from  which  they  are 
derived  in  a general  northeast-southwest  direction  through  the 
county.  The  names  applied  to  these  minor  divisions  indicate 
the  formations  from  which  they  are  chiefly  derived.  The  loca- 
tion of  these  divisions  is  indicated  on  the  sketch  map  (Fig.  2). 

The  Glenrose  Hills:  That  part  of  the  county  northwest  of 

the  Balcones  Escarpment,  forming  the  eastern  margin  of  the 
Edwards  Plateau,  may  be  known  as  the  Glenrose  hills.  The 
underlying  formation,  the  Glenrose,  has  here  been  cut  into  by 
the  headwaters  of  many  small  streams  forming  steep  sloping  hills 
and  rock-filled  stream  channels.  This  formation  includes 
alternating  hard  and  soft  layers  which  weather  on  the  slopes  to 
a succession  of  small  benches  giving  the  hillsides  a characteristic 
terraced  appearance.  Each  terrace  or  bench  is  as  a rule  small, 
corresponding  to  soft  layers  of  from  one  to  a few  feet  in  thick- 
ness. The  slopes  thus  come  to  present  the  appearance  of  having 
been  cultivated,  the  rows  of  planting  having  seemingly  followed 
the  contours  of  the  hill.  The  vegetation  in  this  area  is  chiefly 
low  trees  and  shrubs.  The  predominating  small  tree  is  the 
mountain  cedar  or  juniper,  although  in  addition  there  are  many 
small  oak  and  other  shrubby  trees.  The  maximum  elevation  in 
this  area,  which  is  also  the  maximum  for  the  county,  is  perhaps 
somewhat  more  than  1500  feet  above  sea  level.  The  range  in 


Geology  and  Mineral  Resources  of  Bexar  County  15 


elevation  from  the  higher  hills  to  the  stream  valleys  is  from  200 
to  300  feet. 

The  Edwards  Flint  Hills : Adjoining  the  Glenrose  hills  on  the 
southeast  is  a belt  of  hilly  country  in  which  flint  rock  is  ex- 
tremely abundant  in  the  soils  and  surface  debris.  This  area 
stands  at  a somewhat  lower  level  than  the  Glenrose  Hills.  The 


/ 


Fig. 2. — Sketch  map  to  show  the  minor  physiography  divisions  in 
Bexar  County. 

prevailing  rock  is  the  Edwards  limestone  from  wdiich  the  flints 
have  been  derived  by  weathering.  The  timber  growth  of  this 
area  is  juniper  and  small  oaks.  The  soils,  especially  those 
derived  from  the  flinty  phases  of  the  limestone,  are  often  red, 


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University  of  Texas  Bulletin 


and  the  belt  is  known  locally  as  the  “red  lands”.  The  area 
forms  a narrow  belt  lying  next  to  and  southeast  of  the  Balcones 
Escarpment.  Near  the  west  boundary  of  the  county  this  belt 
narrows  to  such  an  extent  as  not  to  be  appreciable.  In  the 
central  and  eastern  part  of  the  county,  on  the  other  hand,  it 
enlarges  to  a belt  of  three  or  four  miles  in  width,  being  approx- 
imately coincident  with  the  surface  exposures  of  the  Edwards 
formation  as  indicated  on  the  geologic  map.  The  Peter  Clausen 
ranch  in  the  northeastern  part  of  the  county  lies  very  largely 
within  this  belt. 

The  Del  Rio  Plain:  The  soft  materials  of  the  Del  Rio  forma- 
tion, chiefly  clays,  weather  rapidly  when  exposed  at  the 
surface,  and  the  outcropping  belt  of  this  formation  is  repre- 
sented in  the  surface  features  by  a valley  or  low  plain.  Lateral 
streams  frequently  follow  the  strike  of  this  formation  and  for 
that  reason  the  plain  developed  from  this  formation  is  fre- 
quently merged  with  or  obscured  by  stream  terrace  deposits. 
At  both  the  west  and  east  boundaries  of  Bexar  County  the 
clays  of  this  formation  have  but  a limited  surface  outcropping 
and  the  plain  developed  from  them  is  inconspicuous.  In  the 
central  part  of  the  county,  however,  particularly  on  the  Bab- 
cock and  Fredericksburg  roads,  the  belt  of  exposures  of  this 
clay  is  much  widened,  representing  here  successive  exposures  of 
this  formation,  interrupted  by  occasional  belts  of  exposures 
of  the  Buda  limestine.  The  predominating  timber  growth  on 
the  Del  Rio  Plain  is  mesquite,  while  the  intervening  Buda 
limestone  belts  are  characterized  by  a heavy  growth  of  live 
oak.  This  belt  is  crossed  on  the  Fredericksburg  Road  from 
10  to  15  miles  from  San  Antonio. 

The  Austin  Hills:  In  the  central  part  of  Bexar  County  are 

some  belts  of  prominent  hills  trending  northeast-southwest. 
These  hills  are  conspicuous  because  of  a heavy  growth  of  live 
oak  trees  thus  differing  on  the  one  hand  from  the  prevailing 
mesquite  growth  of  the  plains,  and  on  the  other  from  the 
juniper  of  the  hills  of  the  Balcones  Escarpment.  These  hills 
mark  the  outcropping  belts  of  the  hard  rock  or  basal  phase 
of  the  Austin  formation,  combined  in  some  instances  with  the 
Buda  and  Eagle  Ford  formations.  There  are  several  of  these 
belts  of  hills  representing  successive  or  repeated  exposures  of 


Geology  and  Mineral  Resources  of  Bexar  County  17 

this  phase  of  the  formation.  When  followed  to  the  southwest, 
these  belts  of  hills  are  found  to  terminate,  giving  place  to 
lower,  mesquit.e-covered  land.  This  limitation  in  this  direction 
is  due  to  the  southwest  plunge  of  the  structures,  as  sub- 
sequently explained,  by  which  this  phase  of  the  Austin  forma- 
tion is  carried  below  surface  level. 

One  belt  of  these  hills  in  western  Bexar  County  is  seen  lying 
between  the  C’astroville  and  Culebra  roads.  To  the  southwest, 
this  belt  of  hills  narrows  and  terminates  in  Medina  County. 
To  the  northeast,  on  the  other  hand,  the  belt  widens  and 
forms  the  broad  belt  of  hills  of  the  west-central  part  of  the 
county,  entered  on  the  Fredericksburg  road  about  eight  miles 
from  San  Antonio.  A second  belt  of  similar  hills,  originating 
near  San  Pedro  Park  in  San  Antonio,  passes  to  the  northeast. 
These  hills,  which  approximately  parallel  the  San  Antonio- 
Austin  Road,  are  crossed  by  the  Perin-Beitel  Road  from  Fratt 
to  Wetmore. 

The  Taylor-Navarro  Plain:  The  relatively  non-resistant  strata 
of  the  late  Cretaceous,  including  the  upper  part  of  the  Austin 
and  the  Taylor  and  Navarro  formations,  form  extensive  plains. 
Much  of  this  plain  has  subsequently  become  covered  with 
terrace  gravel  deposits,  and  in  places  has  been  much  cut  into 
by  stream  erosion.  However,  it  may  be  regarded  as  a single 
plain  known  as  the  Taylor-Navarro  Plain.  When  not  in- 
fluenced by  terrace  gravel  deposits,  the  soils  on  this  plain  are 
black  and  in  wet  weather  very  sticky.  The  predominating 
timber  growth  is  mesquite.  This  type  of  country  includes  a 
wide  belt  passing  through  the  central  part  of  the  county. 
In  addition  to  this  main  belt  there  are  finger-like  extensions 
of  this  plain  to  the  northeast,  lying  between  ranges  of  Austin 
Hills.  One  such  extension  of  the  plain  is  followed  by  the 
International  and  Great  Northern  Railroad  from  San  Antonio. 
Another  notable  northeastward  extension  from  the  large  plain 
is  at  the  west  side  of  the  county  on  and  near  the  Culebra 
Road.  The  plain  is  here  gravel-covered,  but  is  without  doubt 
underlain,  as  indicated  by  well  records,  by  the  Taylor  forma- 
tion. On  the  northwest  the  plain  is  limited  by  the  foothills  of 
the  Balcones  Escarpment  where  exposures  are  found  of  the 
Austin  and  older  formations.  To  the  southeast  the  plain  ex- 


2-Bex. 


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University  of  Texas  Bulletin 


tends  to  the  range  of  Austin  Hills  already  referred  to.  When 
followed  to  the  northeast  the  plain  narrows  and  terminates 
within  a few  miles  of  Helotes  Creek.  To  the  southwest,  on 
the  other  hand,  it  broadens  and  in  Medina  County  coalesces 
with  the  larger  plain  beyond  the  termination  of  the  belt  of 
Austin  Hills. 

The  Midway -Wilcox  Hills:  The  areas  underlain  by  the  Ter- 

tiary formations  in  this  county  are  characterized  by  more  sandy 
soils  than  those  of  the  Cretaceous  areas.  The  belt  of  country 
underlain  by  the  Midway  and  Wilcox  formations  includes  low 
hills  together  with  areas  of  level  lands.  The  predominating 
timber  growth  is  mesquite.  The  soils  derived  from  the  Mid- 
way formation  are  brown  or  dark  in  color,  while  those  from 
the  Wilcox  are  distinctly  sandy  and  frequently  are  red  in 
color. 

The  Carrizo  Sand  Hills : The  surface  exposures  of  the  Car- 
rizo  formation  are  characterized  by  low  hills  and  very  sandy 
soils.  The  vegetation  on  the  hills  is  chiefly  deciduous  oaks. 
In  Bexar  County  the  sand  hills  of  this  belt  occupy  a limited 
area  in  the  southern  part  of  the  county. 

Stream  Terrace  Plains : A prominent  feature  of  the  Coastal 
Plains  part  of  the  county  is  the  river  flood  plains.  These 
stream  deposits  are  of  different  ages,  from  Pliocene  or  early 
Pleistocene  to  Recent.  They  are  found  likewise  at  different 
levels,  and  many  of  them  have  been  cut  into  by  erosion. 
Some  of  the  larger  plains  are  those  on  which  Kelly  and  Brooks 
aviation  fields  are  located.  These  plains  are  described  in 
connection  with  the  discussion  of  the  Pleistocene  geology. 


Geology  and  Mineral  Resources  of  Bexar  County  19 

STRATIGRAPHIC  GEOLOGY. 

The  formations  exposed  at  the  surface  in  Bexar  County  are 
those  of  the  Mesozoic  and  Cenozoic  eras.  The  Mesozoic  rocks 
of  this  county  are  those  of  the  Lower  and  Upper  Cretaceous 
(Comanchean  and  Cretaceous  systems),  this  division  of  geo- 
logic time  being  well  represented.  The  Cenozoic  deposits  are 
those  of  the  Eocene,  together  with  terrace  deposits  of  the 
Pleistocene.  For  convenience  of  reference  the  formations 
found  in  the  county  are  listed  in  the  table  which  follows.  Al- 
though not  exposed  at  the  surface,  pre-Cretaceous  formations  are 
reached  by  deep  wells  in  the  northern  part  of  Bexar  County. 

PRE-CRETACEOUS 

Two  of  the  wells  of  Bexar  County  of  which  records  have 
been  obtained  have  passed  entirely  through  the  Cretaceous 
formations  and  into  older  deposits.  Of  these  two  wells  one  is 
located  on  the  Leon  Springs  Reservation  north  of  the  Balcones 
fault  zone,  while  the  other  is  on  the  Camp  Bullis  Reservation  a 
few  miles  south  of  the  first  fault  of  that  zone.  Both  wells 
were  drilled  in  an  effort  to  obtain  an  adequate  water  supply 
for  the  Leon  Springs  Government  reservation,  and  in  each 
of  the  wells  the  rocks  lying  next  below  the  Cretaceous  were 
found  to  be  schists.  In  the  well  north  of  the  Balcones  fault 
zone  the  schists  below  the  Comanchean  formation  were 
entered  at  about  1015  feet  below  the  surface  and  were  pene- 
trated 1500  feet,  or  to  the  total  depth  below  the  surface  of 
2500  feet.  Among  pebbles  from  the  basal  part  of  the  Coman- 
chean in  this  well,  Dr.  J.  A.  Udden,  who  has  studied  the 
cuttings,  recognizes  pebbles  resembling  fragments  of  the 
Hickory  formation  of  the  Central  Mineral  region;  also  a few 
flint  pebbles,  dark  in  color  and  laminated  like  pebbles  from  the 
Bend  series.  With  regard  to  the  schists,  he  says,  “Samples 
45  to  49  inclusive  (representing  cuttings  from  the  schists)  are 
most  probably  pre-Carboniferous,  and  in  my  opinion  they  are 
identical  with  similar  material  described  from  below  1100  feet 
in  the  boring  at  Georgetown  in  Williamson  County”.  (MSS.) 

The  second  well  reaching  into  the  pre-Cretaceous,  on  the 
Camp  Bullis  Reservation,  is  south  of  the  Balcones  Escarpment 
and  within  the  fault  zone.  In  this  well  the  schists  were  reached 
at  the  depth  of  1790  feet  and  were  penetrated  115  feet,  or  to 
the  total  depth  below  the  surface  of  1905  feet.  With  regard 
to  the  schists  of  this  well,  Dr.  Udden,  who  has  examined 


20 


University  of  Texas  Bulletin 


TABLE  OF  GEOLOGIC  FORMATIONS  IN  BEXAR  COUNTY. 


Formation 

name 

Thick- 

ness 

o 

‘o 

N 

o 

Pleistocene 

Flood- 

plain 

deposits 

100-+- 

fl 

CD 

O 

Eocene 

Carrizo 

Wilcox 

Midway 

? 

600  -f- 
200-t- 

Upper  Cretaceous 

Navarro 

Taylor 

Austin 

Eagleford 

450-+- 

450-f- 

350 

35 

W 

d 

o 

Washita 

Buda 
Del  Rio 
Georgetown 

65 

70 

50-f- 

Mesozoic  • 

<v 

CD 

QJ 

pH 

u 

d 

cd 

a> 

dS 

CD 

Fredericks- 

burg 

! 

Edwards 

Comanche 

Peak 

450  —f— 

9 

i 

a 

o 

D 

Trinity 

Glenrose 
Travis  Peak 

800-+- 
1200  —|— 

Fig.  3.  Table  of  Geologic  formations  together  with  graphic  representa- 
tion of  the  Columnar  section.  Ktp,  Travis  Peak;  Kgr,  Glenrose;  Ke, 
Edwards  including  Georgetown;  Kdr,  Del  Rio;  Kba,  Buda;  Kef,  Eagleford; 
Ka,  Austin  Chalk;  Kt.  Taylor;  Kn,  Navarro;  Em,  Midway;  Ew,  Wilcox;  PI, 
Pleistocene. 


Geology  and  Mineral  Resources  of  Bexar  County  21 

the  samples,  states  that  the  formation  represented  is  probably 
the  Packsaddle  Schists  of  the  Central  Mineral  Region.  (Mss.) 
The  logs  of  these  two  ^ells  are  given  in  the  section  on  well 
records. 

How  far  to  the  east  from  the  Balcones  Escarpment  these 
schists  lie  immediately  below  the  Comanchean  formations  can 
be  determined  only  by  subsequent  drilling.  The  fact  that 
the  schists  have  been  found  under  the  Comanchean  at  George- 
town and  at  San  Antonio  indicates  that  they  underlie  those 
formations  through  a considerable  north  and  south  distance 
along  the  Balcones  fault  zone. 

MESOZOIC 

COMANCHEAN  CRETACEOUS 

The  formations  of  the  Comanchean  series  in  this  county  are 
shown  in  the  table  on  page  20.  They  are  included  on 
the  Trinity,  Fredericksburg  and  Washita  divisions  as  there 
indicated. 

TRAVIS  PEAK  FORMATION 

The  term  Travis  Peak  formation  has  been  applied  by  Hill  to 
the  lowermost  rocks  of  the  Cretaceous  of  south-central  Texas. 
This  formation  represents  in  part  at  least  the  Trinity  or  Base- 
ment sands  of  northern  Texas.  Although  not  exposed  at  the 
surface,  the  Travis  Peak  formation  is  reached  by  some  of  the 
deep  wells  in  the  northern  and  north-central  parts  of  the 
county.  Records  have  been  obtained  of  about  six  wells  in  the 
county  which  pass  into  or  through  this  formation. 

The  well  of  R.  Mercke  at  Bulverde  on  the  Cibolo  River  at 
the  north  line  of  the  county,  is  reported  by  Hill  and  Vaughan* 
as  reaching  a depth  of  361  feet.  The  surface  exposure  at  this 
locality  is  the  Glenrose  formation,  and  on  the  basis  of  the  log, 
Hill  and  Vaughan  have  regarded  this  formation  as  extending 
to  the  depth  of  137  feet.  From  147  feet  to  the  bottom  of  the 
well,  361  feet,  the  formation  is  identified  by  them  as  Travis 
Peak. 

A well  drilled  on  the  Leon  Springs  Reservation  in  this  county 
in  1909,  starting  in  the  Glenrose  formation,  passed  entirely 
through  the  Travis  Peak  formation  and  into  underlying  schists. 
Samples  of  the  cuttings  from  the  well  were  submitted  to  the 


*18th  Ann.  Rept.,  pt.  2,  U.  S.  Geol.  Surv.,  p.  272,  1898. 


22 


University  of  Texas  Bulletin 


Bureau  of  Economic  Geology  and  were  examined  by  Dr.  J.  A. 
Udden.  A log  of  the  well  and  supplementary  data  were  sent  to 
the  Bureau  by  Mr.  Alexander  Deussen.  The  record  from  this 
well,  which  is  of  especial  importance  in  determining  the  thick- 
ness of  the  Glenrose  and  Travis  Peak  formations,  is  given  on  a 
later  page.  Prom  the  surface  to  the  depth  of  1025  feet,  the 
cuttings  from  this  well  are  identified  by  Dr.  Udden  as  Coman- 
chean.  Mr.  Alexander  Deussen  has  assigned  the  strata  from 
535  feet  to  1015  feet  to  the  Travis  Peak, . indicating  for  the 
formation  a thickness  of  about  480  feet. 

The  third  well  passing  into  this  formation  is  also  a Gov- 
ernment well  located  on  the  Camp  Bullis  Reservation,  six 
miles  south  and  one-half  mile  east  of  the  well  on  the  Leon 
Springs  Reservation.  In  this  well  the  combined  thickness  of 
the  Glenrose  and  Travis  Peak  formations,  including  Basement 
sand,  amounts  to  between  1200  and  1300  feet. 

A fourth  well  believed  to  enter  or  pass  through  the  Travis 
Peak  formation  was  drilled  on  the  Waring  Estate  near  the 
Bandera  Road,  seven  and  one-half  miles  northwest  of  San 
Antonio.  Of  this  well  there  is  preserved  the  driller’s  log, 
but  unfortunately  no  samples  of  the  cuttings.  A blue  print 
record  of  the  log  of  the  well  has  been  obtained  from  the  Con- 
structing Quartermaster’s  office  at  Fort  Sam  Houston.  The 
data  for  the  log  were  preserved  and  the  blue  print  record  made 
at  the  time  the  well  was  drilled  by  Mr.  F.  A.  Gartner.  In  this 
well  the  Comanchean  formations  were  entered  at  400  feet  from 
the  surface.  The  well  was  drilled  to  the  depth  of  2853  feet, 
thus  penetrating  2453  feet  of  Comanchean  or  older  sediments. 
The  Ridder  well  on  the  Medina  River  southwest  of  San  An- 
tonio and  the  Kearney  Pipe  Line  and  Oil  Company  well  south 
of  Leon  Creek,  record  of  which  is  subsequently  given,  probably 
terminate  in  the  Travis  Peak  formation. 

As  indicated  by  the  drillers’  logs  and  more  particularly  by 
the  cutings  from  these  wells,  the  Travis  Peak  formation  under- 
lying Bexar  County  includes  layers  of  limestone  alternating 
with  softer  layers,  chiefly  of  marly  clays.  The  limestones, 
as  indicated  by  the  well  on  the  Leon  Springs  Reservation,  in- 
clude both  ordinary  and  dolomitic  layers,  while  the  marly 
clays  frequently  contain  pyrite.  A phase  of  this  formation  is 
recorded  in  the  logs  as  “red  mud”  or  “red  clay”.  The  samples 
of  cuttings  seem  to  indicate  that  the  layers  so  recorded  include 


Geology  and  Mineral  Resources  of  Bexar  County  23 

rather  soft  calcareous  clays  or  marls  with,  in  some  instances,  a 
calcareous  and  • ferruginous  cement,  together  with  fine  sands 
or  silts. 

As  this  formation  lies  unconformably  on  the  pre-Cretaceous, 
its  thickness  may  be  expected  to  vary  exceedingly.  Of  the 
structure  and  rate  of  dip  of  the  formation,  very  little  can  be 
determined  from  the  scanty  records  now  available.  North  of 
the  Balcones  fault  zone  it  is  to  be  expected  that  the  formation 
will  conform  to  the  Glenrose  and  have  a similar  moderate 
southeast  dip.  In  that  part  of  the  county  within  and  east  of 
the  Balcones  fault  zone,  it  is  to  be  expected  that  this  forma- 
tion shares  in  the  disturbed  conditions  common  to  the  other 
formations  of  that  belt,  which  are  more  fully  described  else- 
where. 

GLENROSE  FORMATION 

The  Glenrose  formation  of  the  Lower  Cretaceous  (Comanchean) 
age,  is  the  oldest  of  the  formations  exposed  at  the  surface  in  this 
county.  This  formation  includes  chiefly  alternating  layers  of 
moderately  hard  and  soft  rocks.  The  harder  ledges  are  chiefly 
limestone,  as  this  formation  contains  almost  no  flint.  Some  of 
the  limestone  layers  are  fine-grained  and  quite  hard,  although 
as  a rule  the  limestones  of  this  formation  are  of  but  medium 
hardness.  The  marl  layers  of  the  formation  are  usually  thin, 
being  from  a few  inches  to  one  or  two  feet  thick,  and  rather 
soft.  At  the  surface  the  marl  layers,  like  the  limestone  ledges, 
are  usually  yellow.  When  buried  within  the  earth,  they  may  be 
at  times  gray  or  blue.  The  formation  may  usually  be  recognized 
by  the  characteristic  succession  of  hard  and  soft  strata,  although 
in  places  the  formation  is  more  heavily  bedded.  Occasionally 
also,  the  heavy  limestone  ledges  are  honey-combed  and  under 
these  conditions  resemble  the  non-flinty  ledges  of  the  overlying 
Edwards  formation.  The  examination  of  any  considerable  sec- 
tion, however,  will  usually  afford  a basis  for  separation  from  the 
Edwards  formation. 

The  marls  of  this  formation  have  been  used  in  road-making 
on  some  of  the  roads  passing  through  this  area  where  other  ma- 
terials are  not  readily  available.  The  calcium  sulphate  mineral, 
celestite,  is  occasionally  found  filling  cavities  in  this  formation, 


24 


University  of  Texas  Bulletin 


and  has  been  mined  to  a limited  extent  near  Austin,  in  Travis 
County.  The'  sub-surface  layers  of  the  formation  produce  mod- 
erate supplies  of  water,  and  many  of  the  wells  yielding  moderate 
supplies  north  of  the  Balcones  fault  zone  terminate  in  this 
formation. 

Thickness : The  fact  that  the  base  of  the  Glenrose  formation 
is  nowhere  exposed  in  this  county  makes  it  impossible  to  measure 
the  thickness  of  the  formation  from  surface  exposures.  By 
combining  surface  exposures  and  well  records,  however,  it  is 
possible  to  determine  the  thickness  of  this  formation  probably 
within  reasonably  close  limits.  Perhaps  the  most  trustworthy 
measurement  of  the  thickness  of  the  formation  in  this  county 
is  that  obtained  on  the  Leon  Springs  Military  Reservation.  In 
the  deep  well  on  the  reservation,  as  already  noted,  the  Glenrose 
is  regarded  as  extending  from  the  surface  to  a depth  of  535 
feet.  In  the  hills  near  the  well,  the  Edwards  limestone  is  pro- 
visionally identified  as  coming  into  the  section  at  about  the  1420 
foot  level.  The  ground  level  at  the  well  is  about  1156  feet  above 
sea  level.  Hence  to  the  535  feet  of  this  formation  penetrated  in 
the  well  must  be  added  between  265  and  315  feet  exposed  at  the 
surface,  making  a total  thickness  for  this  formation  of  about 
800  feet.  This  measurement,  however,  may  include  the  equiva- 
lent of  the  Walnut  clays  and  the  Comanchean  Peak  limestone; 
which,  however,  are  of  limited  development  in  this  county. 

Physiographic  expression:  The  alternately  hard  and  soft 

strata  of  this  formation  gave  rise  in  the  early  literature  to  the 
term  ‘ ‘ alternating  beds”  as  applied  to  the  formation.  This  suc- 
cession of  hard  and  soft  layers  occasions  the  characteristic  ter- 
raced appearance  already  referred  to  as  distinguishing  the  Glen- 
rose Hills. 

Common  fossils:  Among  the  fossils  found  in  considerable 

abundance  in  the  Glenrose,  the  most  frequently  met  with  are  the 
gastropod  Lunatia  ( Tylostoma ) pedernalis  and  the  bivalve 
Cyprinaf  mediate.  Neither  of  these,  however,  is  confined  to  the 
Glenrose  since  both  are  found  likewise  in  the  Travis  Peak  forma- 
tion. 

COMANCHE  PEAK  FORMATION 

The  Comanche  Peak  limestone  has  not  been  differentiated  as 


Geology  and  Mineral  Resources  of  Bexar  County  25 

a formation  in  this  county,  and  in  the  mapping  and  in  the 
measurement  of  sections  it  is  included  either  with  the  Glenrose 
or  with  the  Edwards.  According  to  Hill  and  Vaughan  this 
formation  is  present  in  the  Austin  quadrangle  to  the  northeast 
of  this  county  and  likewise  in  the  Uvalde  quadrangle  to  the 
southwest,  where  it  is  a nodular,  somewhat  massive  limestone, 
containing  the  oyster  Exogyra  texana.  In  these  quadrangles 
the  formation  has  a thickness  of  from  50  to  60  feet.  Hence, 
although  not  yet  differentiated,  it  is  probably  present  also  in 
Bexar  County. 


EDWARDS  FORMATION 

The  Edwards  formation  consists  chiefly  of  limestones.  The 
rock  of  the  formation  as  developed  in  this  county  is  usually 
coarsely  crystalline,  although  in  this  respect  it  is  variable,  some 
parts  of  the  formation  being  particularly  dense  and  of  fine 
texture,  approaching  a lithographic  stone  in  structure.  Fre- 
quently both  on  surface  exposures  and  deep  within  the  earth, 
as  indicated  by  well  borings,  the  formation  is  profoundly  honey- 
combed and  cavernous.  These  openings  in  the  rock,  where  ex- 
posed in  quarrying  the  limestone,  follow  more  or  less  the  bedding 
planes  and  joint  planes  of  the  formation.  The  Edwards  forma- 
tion is  especially  characterized  by  a great  abundance  of  flints 
enclosed  within  the  limestone.  These  flints  are  in  the  form  of 
layers  which  lie  parallel  with  the  bedding  planes,  or  replace  for 
a considerable  space  the  limestone  layers  of  the  formation.  Some 
of  the  flint,  however,  is  in  the  form  of  nodules,  oval  or  flattened 
masses,  or  so-called  “boulders”  in  the  limestone.  Upon  the 
disintegration  of  the  limestone,  the  flints  remain  on  the  surface 
in  great  profusion.  Usually  the  Edwards  limestone  may  be 
recognized  by  the  presence  of  these  flint  masses  both  in  the  rock 
when  seen  in  place,  and  in  the  residue.  The  soils  derived  from 
the  flinty  phase  of  the  Edwards  formation  are  prevailingly  red, 
and  the  belt  of  country  occupied  is  referred  to  locally  as  the 
“red  lands.”  In  parts  of  this  formation,  however,  the  flints 
are  less  abundant  and  exposures  may  frequently  be  met  with  in 
which  no  flints  are  observed.  In  the  absence  of  fossils  some 
difficulty  may  be  experienced  in  separating  such  exposures  from 


26 


University  of  Texas  Bulletin 


the  hard  phases  of  the  Glenrcse  on  the  one  hand,  and  the  Buda 
on  the  other.  If  in  such  exposures  the  texture  is  found  to  be 
coarsely  crystalline,  the  rock  may  be  quite  definitely  separated 
from  the  Buda,  which  never  presents  this  appearance  in  this 
county.  If,  on  the  other  hand,  the  rock  is  close-grained,  dense 
and  of  fine  texture,  the  separation  from  the  Buda  can  perhaps 
be  safely  made  only  on  the  fauna.  . 

Aside  from  the  flint  masses  which  it -contains,  the  Edwards 
limestone  is  for  the  most  part  a very  pure  calcium  carbonate. 
It  is  also,  as  previously  noted,  a very  dense,  hard,  partly  crys- 
tallized limestone.  These  characteristics  make  it  valuable  for  a 
number  of  purposes.  Several  quarries  have  been  opened  in  this 
formation  in  Bexar  County  for  the  manufacture  of  lime.  Bock 
from  this  formation  is  taken  from  a quarry  at  Beckman  for  use 
as  rip-rap  in  Government  work  on  the  harbors  of  the  Gulf  coast. 
The  hard,  dense  rock  of  the  Edwards  formation,  when  crushed, 
should  afford  material  favorable  for  concrete,  although  so  far 
as  observed  no  part  of  the  formation  is  being  so  used  at  the 
present  time,  owing  perhaps  to  the  abundance  of  concrete  ma- 
terial in  this  county.  This  rock  should  be  of  service  also  in 
road-building.  Upon  partial  decay  the  rock  in  places  assumes  a 
soft,  spongy  appearance/  This  form  of  the  rock  has  been  used  in 
road-building  on  the  Bulverde  and  Blanco  roads. 

Thickness : A full  measure  of  the  thickness  of  the  Edwards 
formation  has  not  been  obtained  from  surface  exposures  in  this 
county,  but  from  well  records  the  thickness  of  the  formation  is 
estimated  to  be  between  400  and  500  feet. 

Physiographic  Expression:  The  belt  of  country  occupied  by 

the  Edwards  formation  is  moderately  to  distinctly  hilly,  although 
in  places  there  are  areas  of  relatively  level  lands.  The  native 
vegetation  is  chiefly  juniper  and  small  oaks,  including  in  places  a 
limited  amount  of  mesquite.  The  surface  materials  from  the 
formation,  as  already  noted,  contain  quantities  of  flint.  The 
soils,  especially  those  derived  from  the  flinty  phases  of  the 
formation,  are  characteristically  red  in  color.  The  soil  supports 
a good  growth  of  grass  and  these  lands  form  desirable  ranch 
lands  and  are  used  chiefly  for  this  purpose. 

Common  fossils : Although  not  always  abundant,  several  of 


Geology  and  Mineral  Resources  of  Bexar  County  27 

the  fossils  of  the  Edwards  formation  are  very  unusual  in  ap- 
pearance. This  is  true  in  particular  of  the  bizarre  mollusks  of 
the  genera  Radiolites,  Monopleura , and  Requienia. 

Surface  exposures  and  local  details:  The  surface  exposures 

of  the  Edwards  limestone  form  a belt  varying  in  width,  lying 
immediately  south  of  the  Glenrose  area  and  hence  at  the  north- 
ern margin  of  the  Balcones  fault  zone.  This  belt  is  widest  at 
the  eastern  margin  of  the  county  and  narrows  towards  the  west. 
Where  crossed  by  the  Bulverde  Road,  in  the  eastern  part  of  the 
county,  this  belt  of  the  Edwards  formation,  including  possibly 
the  Georgetown;  has  a width  of  over  live  miles.  On  the  Blanco 
Road  the  belt  is  somewhat  narrowed.  At  the  Fredericksburg  and 
Babcock  road-crossing,  the  belt  is  further  narrowed,  and  at  the 
Bandera  Road  crossing  has  a width  not  exceeding  one-half  mile. 

At  the  pit  of  the  San  Antonio  Lime  Company,  on  the  Fred- 
ericksburg Road  16  miles  from  San  Antonio,  the  limestones  of 
the  Edwards  formation  are  well  stratified,  consisting  of  layers  of 
hard  rock  varying  from  a few  inches  to  four  or  live  feet  in 
thickness.  Some  layers  of  the  rock  contain  numerous  small 
cavities  produced  by  ground  water.  Flint  layers  are  present 
usually  lying  parallel  with  the  bedding  planes,  although  flint 
concretions  are  seen,  and  occasionally  flint  deposits  are  found 
filling  joint  planes.  The  solution  cavities . also  are  more  or  less 
lined  with  silica.  The  limestone  rock  is  heavy  and  upon  close 
examination  is  seen  to  be  in  places  minutely  banded. 

The  right  bank  of  Helotes  Creek  below  the  Bandera  Road 
crossing  affords  a good  exposure  of  this  formation.  The  creek 
here  follows  on  or  near  the  main  fault  line  separating  the  Glen- 
rose and  the  Edwards  formations. 

GEORGETOWN  FORMATION 

Lithologically  the  Georgetown  formation  if  present  in  this  area 
is  very  similar  to  the  Edwards,  and  in  the  mapping  and 
columnar  section  these  formations  are  not  separated.  This 
treatment  of  the  two  formations  has  seemed  the  more  necessary 
since  in  well  logs  there  is  almost  no  opportunity  to  separate 
them.  An  exposure  which  probably  represents  the  Georgetown 
is  seen  on  the  Bandera  Road,  17  miles  from  San  Antonio.  The 


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University  of  Texas  Bulletin 


limestone’  rock  exposed  here,  lying  immediately  below  the  Del 
Rio  clay,  is  a very  hard,  close-grained  rock,  containing  little  or 
no  flint.  In  the  eastern  part  of  the  connty  a similar  rock  is  seen 
lying  below  the  Del  Rio  on  the  Peter  Clansen  ranch,  1 y2  mile 
north  of  the  Nacogdoches  Road.  The  Georgetown  formation  in 
the  Colorado  River  section  is  reported  to  have  a thickness  of 
from  65  to  70  or  80  feet.  In  the  Uvalde  folio  the  formation  is 
estimated  by  Yanghan  to  have  possibly  a thickness  of  40  feet. 
These  two  formations,  the  Edwards  and  Georgetown,  are  of 
special  economic  importance  in  this  connty  as  the  chief  large 
water-bearing  formations  of  the  area. 

DEL  RIO  FORMATION 

The  Del  Rio  formation  consists  largely  of  clays  which  on 
surface  exposure  are  usually  yellow,  but  when  encountered  below 
the  surface  are  usually  blue  in  color.  The  clays  of  this  formation 
contain  in  places  great  numbers  of  fossils,  especially  of  the 
small  oyster  Exogyra  arietina.  Occasionally  these  shells  are 
cemented  together  by  calcareous  or  ferruginous  cement  forming 
indurated  layers  within  the  clay  beds.  The  formation  contains 
more  or  less  iron  sulphide  as  pyrite  and  in  well  cuttings  the 
amount  of  pyrite  is  not  infrequently  found  to  be  considerable. 
On  the  surface  exposures  gypsum  in  small  quantities  is  not  in- 
frequently observed  in  the  clay. 

Thickness:  No  surface  exposure  has  been  found  in  this  county 
in  which  the  whole  thickness  of  this  formation  can  be  measured. 
In  the  records  of  wells,  however,  the  formation  is  quite  uniformly 
reported  as  having  a thickness  of  from  50  to  70  feet.  Rarely 
does  the  reported  thickness  of  the  formation  fall  below  or  rise 
above  these  limits.  In  Bexar  County  this  formation  is  quite 
generally  known  to  the  well  drillers  as  the  “mud  hole”  or  the 
“second  mnd”,  cr  the  “big  mud”.  These  names  have  origi- 
nated because  of  the  character  and  position  of  the  formation.  It 
is  known  as  the  “mud  hole”  because  the  clay  when  churned  up 
by  the  drill  becomes  mud.  The  term  “second  mud”  is  sometimes 
applied  to  it  because  a formation  at  a higher  level,  the  Eagle- 
ford,  frequently  contains  enough  clay  to  cause  cable  tools  to 
stick,  and  hence  gives  the  formation  the  character  of  mud.  The 


Geology  and  Mineral  Resources  of  Bexar  County  29 

origin  of  the  term  ‘‘big  mud”  is  similar.  As  the  Del  Rio  forma- 
tion has  a thickness  of  from  50  to  70  feet  while  the  clayey  phase 
of  the  Eagleford  rarely  exceeds  30  to  35  feet,  the  Del  Rio  has 
come  come  to  be  known  as  the  “big  mud”. 

Physiographic  expression:  The  Del  Rio  formation,  being 

chiefly  a relatively  non-resistant  clay  lying  between  relatively 
resistant  limestones  '(the.  Georgetown-Edwards  series  below  and 
the  Buda  limestone  above),  is  found  as  a rule  on  surface  ex- 
posures to  occupy  a valley,  or  the  abrupt  slope  from  an  upland 
to  the  valley.  The  soils  derived  from  this  formation  are  black  or 
brownish  in  color.  The  timber  growth  is  chiefly  mesquite,  and 
frequently  the  Del  Rio  outcrop  when  in  a valley  may  be  followed 
by  the  dense  growth  of  mesquite,  differing  in  this  respect  from 
the  mixed  growth  of  timber,  chiefly  oak  and  juniper,  found  on 
the  hard  phases  of  the  limestone  formations. 

Common  fossils : As  already  noted,  the  small  oyster,  Exogyra 
arietina , is  a very  characteristic  index  fossil  of  this  formation, 
and  its  stratigraphic  equivalents.  This  fossil  is  particularly 
abundant  in  the  lower  part  of  the  formation.  Near  the  top  the 
deposits  become  relatively  unfossiliferous.  A fossil  occasionally 
found  in  the  upper  part  of  the  formation  is  the  oyster,  Gryphea 
mucronata.  Lithologically,  the  beds  change  somewhat  towards 
its  upper  limit,  becoming  more  calcareous  and  including  in  places 
shelly  lime  rock.  Near  the  contact  with  the  Buda  is  seen  occa- 
sionally a soft,  light-colored  phase  of  the  formation  superficially 
resembling  in  a degree  the  partially  disintegrated  phases  of  the 
Eagleford  formation. 

Surface  exposures  and  local  details : The  surface  exposures  of 
the  Del  Rio  formation  are  found  throughout  a belt  of  country 
next  south  of  the  exposure  of  the  Georgetown-Edwards  forma- 
tions. The  formation  being  thin,  this  belt  of  surface  outcropping 
is  relatively  narrow,  usually  not  exceeding  a half  mile.  There 
are,  however,  some  localities  where  the  belt  of  surface  exposures 
of  this  formation  is  widened,  owing  to  minor  faulting,  which 
brings  the  formation  successively  to  the  surface.  This  belt  of 
minor  faulting  is  crossed  on  the  Fredericksburg  Road  from  10.2 
to  13.2  miles  from  San  Antonio,  and  on  the  Babcock  Road  from 
12  to  15  miles  from  San  Antonio.  Within  this  belt  on  the  Fred- 


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ericksburg  Road,  owing  to  a combination  of  faulting  and  folding 
together  with  variations  in  surface  level,  the  Del  Rio  formation 
shows  itself  in  five  successive  belts  as  follows:  First  belt,  from 
10.2  to  10.3  miles  from  San  Antonio;  second  belt,  from  10.5  to 
10.7 ; third  belt,  from  11.4  to  11.6 ; fourth  belt,  from  11.9  to  12.3 ; 
fifth  belt,  from  12.7  to  13.2  miles.  On  the  Babcock  Road,  suc- 
cessive belts  of  this  formation  come  in  as  follows : First  belt, 
12.05  to  12.1  miles  from  San  Antonio;  second  belt,  12.4 -to  12.5; 
third  belt,  12.6  to  12.7 ; fourth  belt,  12.8  to  12.85 ; fifth  belt, 
Valley  of  Leon  Creek  probably  occupied  chiefly  by  this  forma- 
tion, about  13  to  13.5  miles. 

The  formations  alternating  with  the  Del  Rio  in  these  ex- 
posures are  the  underlying  Georgetown-Edwards  and  the  over- 
lying  Buda,  including  the  Eagleford  and  a part  of  the  Austin. 
As  already  stated,  the  successive  exposures  of  the  formation  are 
due  in  part  to  faulting  and  in  part  to  changes  in  the  surface 
elevation. 

East  of  the  Leon  Springs  Reservation  in  this  county  and  also 
west  of  the  . Bandera  Road,  this  formation  so  far  as  observed 
appears  as  but  a single  belt  with  usually  but  few  actual  surface 
exposures.  On  the  Blanco  Road  the  belt  is  crossed,  without  any 
observed  exposures  immediately  on  the  road,  at  about  12  miles 
from  San  Antonio.  On  the  Bulverde  Road,  the  Buda  formation 
is  well  exposed  at  the  foot  of  a north-sloping  hill  13.5  miles 
from  San  Antonio.  Although  no  exposures  of  the  Del  Rio  clays 
are  seen  on  the  road,  this  formation  may  be  expected  to  occupy 
the  valley  at  the  foot  of  this  hill  and  to  extend  to  the  limestone 
hills  which  begin  on  this  road  at  about  13  miles  from  San  An- 
tonio. To  the  east  of  the  Bulverde  road  the  Del  Rio  formation 
has  not  been  traced  in  detail,  but  is  to  be  expected  as  a rela- 
tively narrow  belt  extending  as  mapped  in  a general  northeast- 
ward direction  to  the  county  line  at  the  Cibolo  River.  Near  the 
county  line  an  exposure  is  seen  at  a water-tank  on  the  Clausen 
Ranch,  1%  miles  north  of  the  Nacogdoches  Road  crossing  of  the 
Cibolo  River.  West  of  the  Bandera  Road  exposures  of  this 
formation  continue  for  two  or  three  miles,  beyond  which  the 
belt  narrows  and  the  formation  in  places  is  faulted  out  of  sight. 

The  Del  Rio  formation  is  extensively  used  in  its  belt  of  sur- 


Geology  and  Mineral  Resources  of  Bexar  County  31 

face  outcropping  in  the  construction  of  ponds.  On  the  Bandera 
Road  a pond  made  from  this  formation  is  seen  near  Helotes 
Creek  17  miles  from  San  Antonio.  The  clays  of  the  formation 
are  utilized  in  making  a pond  on  the  Clausen  ranch,  near' the 
east  county  line,  1^2  miles  north  of  the  Nacogdoches  Road.  At 
these  localities  the  small  fossil  Exogyra  arietina  is  extremely 
abundant. 

BUDA  FORMATION 

I 

The  Buda  formation  as  developed  in  this  county  is  quite 
uniformly  a close-grained,  dense,  hard  limestone.  On  surface 
exposures  this  rock  is  usually  light-colored,  or  tinged  with  gray, 
yellow,  or  blue.  As  seen  in  well  cuttings,  the  limestone  is 
usually  of  light  color,  although  a part  of  the  formation  fre- 
quently shows  as  a blue  rock;  Black  specks  in  the  limestone  is 
a characteristic  frequently  referred  to  by  drillers  in  describing 
the  cuttings  from  wells.  The  change  in  sedimentation  from  the 
Del  Rio  to  the  Buda  and  from  the  Buda  to  the  Eagleford 
formations  appears  to  have  been  abrupt,  there  being  little  or  no 
gradation  between  the  formations.  The  hard  limstone  of  the 
Buda  formation  lying  between  the  softer  rocks  of  the  Del  Rio 
and  Eagleford  forms  a horizon  both  conspicuous  and  readily 
followed  on  the  surface.  The  Buda  limestone  in  this  county 
is  but  little  utilized  at  the  present  time.  Its  hardness  and  close 
texture  indicate  that  as  here  developed  the  limestone  would  be 
suitable  for  concrete  material. 

Thickness:  Both  in  lithologic  characteristics  and  in  thickness 
the  Buda  formation  is  perhaps  the  least  variable  of  the  Creta- 
ceous formations  as  developed  in  this  county.  Well  records  indi- 
cate that  the  Buda  limestone  is  here  quite  uniformly  between  55 
and  65  feet  thick.  Rarely  is  the  formation  reported  to  vary 
beyond  these  limits. 

Physiographic  expression : In  its  surface  exp'osures  the  Buda 
limestone  appears  as  hard,  thickly  bedded  rock.  The  surface  is 
frequently  rough  owing  to  partial  dissolution  through  the  agency 
of  surface  waters.  The  soils  derived  from  the  formation  are 
dark  colored  and  usually  relatively  thin,  including  many  rock 
fragments.  When  found  capping  hills  the  soils  from  the  Buda 


32 


University  of  Texas  Bulletin 


formation  support  a rather  heavy  growth  of  timber  made  up 
chiefly  of  oaks.  In  this  respect,  the  Buda  formation  resembles 
the  hard  rock  phases  of  the  Austin  formation. 

Common  fossils:  The  Buda  limestone  on  surface  exposures;  is 
usually  found  to  contain  fossils,  sometimes  in  considerable  num- 
ber. The  shells  of  invertebrates  have,  however,  for  the  most 
part  been  replaced  or  filled  with  a mineral  deposit,  probably 
usually  calcite.  Hence  the  fossils  are  seldom  easily  removed 
from  the  matrix,  and  are  with  difficulty  used  in  identifying  the 
formation.  Thin  sections  of  the  rock  have  shown  that  in  this 
formation  are  found  numbers  of  foraminifera.*  Lithologically 
the  formation  may  be  in  a measure  recognized  by  its  uniformly 
close-grained*,  dense  structure,  although  similar  dense  masses  of 
rock  are  found  also  at  places  in  the  Georgetown  and  Edwards 
formations,  and  less  distinctly  so  in  the  hard  rock  phases  of  the 
Austin  formation.  The  position  of  the  Buda  limestone,  lying 
between  the  lithologically  very  different  Del  Rio  and  Eagleford 
formations,  assists  materially  in  locating  this  formation  on  sur- 
face exposures  and  in  well  drillings  determines  its  position 
definitely. 

Surface  exposures  and  local  details : The  Buda  formation  in 
Bexar  County  comes  to  the  surface  in  a relatively  narrow  belt 
having  a general  northeast-southwest  trend.  On  the  Bulverde 
Road  the  rocks  of  this  formation  are  exposed  near  the  base  of  a 
north-sloping  hill  about  13.5  miles  from  San  Antonio.  The  for- 
mation here  dips  into  the  hill  under  the  Eagleford  and  Austin 
formations,  the  belt  of  exposed  rock  being  narrow.  So  far  as 
observed  the  rocks  of  the  Buda  are  not  again  exposed  on  this 
road.  To  the  east  of  the  road  the  line  of  outcropping  of  this 
formation  has  not  been  traced  in  detail  although  it  is  known  to 
continue  in  a general  northeast  direction  to  the  county  line. 

A small  anticline  in  this  formation  is  observed  at  the  Salado 
Creek  crossing  of  the  Blanco  Road.  Just  above  this  crossing  as 
much  as  35  or  40  feet  of  the  Buda  formation  is  exposed  in  the 
right  bank  of  the  stream.  Downstream  the  Buda  disappears  be- 
neath the  Eagleford  and  Austin  formations  within  about  one- 
fourth  mile  below  the  road  crossing.  When  followed  upstream 


*U.  S.  Geol.  Surv.,  18th.  An.  Rpt.  pt.  2,  p.  228,  1898. 


Geology  and  Mineral  Resources  of  Bexar  County  33 

the  rocks  of  the  Buda  formation  are  found  likewise  to  dip  below 
the  stream  level,  giving  place  to  the  Eagleford  and  Austin 
formations  in  the  stream  banks.  However,  the  Buda  reappears 
in  this  stream  within  about  three-fourths  or  one  mile  further 
upstream,  indicating  a relatively  limited  development  of  the  v/est 
slope  of  the  anticline.  On  the  Blanco  Road  the  Buda  is  exposed 
at  the  Salado  Creek  crossing,  and  again  between  eleven  and  one- 
half  and  twelve  miles  from  San  Antonio. 

On  the  Fredericksburg  and  Babcock  roads  the  Buda  formation 
is  found  to  share  in  the  minor  faulting  which,  as  already  men- 
tioned, brings  these  thinner  formations  repeatedly  to  the  surface. 
On  the  Fredericksburg  Road  the  Buda  formation  is  first  met  with 
lying  below  the  Eagleford  formation  a short  distance  beyond 
the  Lockhill-Selma  Cross-road,  about  10.1  miles  from  San 
Antonio.  It  is  last  seen  on  this  road  at  the  Bacon  Ranch  cross- 
road, 12.7  miles  from  San  Antonio.  On  the  Babcock  road  the 
formation  appears  at  intervals  from  12  to  12.9  miles  from  San 
Antonio.  On  both  of  these  roads  this  formation  alternates  by 
changes  in  surface  elevation  and  by  faulting  with  the  Del  Rio 
and  other  formations. 

The  belt  of  Buda  exposures  may  be  seen  at  intervals  as  far 
west  as  the  Hoffman  Ranch,  about  three  miles  west  of  Helotes 
Creek.  Beyond  this  place  the  belt  of  Buda  exposures  narrows 
and  the  formation  shows  but  limited  exposures  to  the  Medina 
County  line.  The  place  of  the  formation  below  the  surface  is 
recorded  in  well  records  throughout  most  of  the  central  part  of 
the  county.  From  its  surface  exposures  the  formation  dips  with 
variations  due  to  faulting  and  folding  toward  the  south  and 
southeast.  At  the  northern  limits  of  the  city  of  San  Antonio 
this  formation  may  be  expected  at  from  300  to  350  feet  beneath 
the  surface,  depending  upon  variations  in  surface  elevation.  At 
the  southern  city  limits,  six  miles  farther  south,  owing  to  steep 
dips  and  faults,  this  formation  lies  much  deeper  and  is  there 
encountered  in  well  drilling  at  between  1200  and  1300  feet.  A 
few  miles  farther  south,  near  the  Chavanneux  Cross-road,  it  is 
found  by  well  drilling  to  be  buried  to  a depth  of  1600  or  1700 
feet. 


3-Bex. 


34 


University  of  Texas  Bulletin 
UPPER  CRETACEOUS 


The  Upper  Cretaceous  series  is  well  represented  in  the 
Bexar  County  section.  The  formations  in  order,  beginning  with 
the  oldest,  are:  Eagleford,  Austin,  Taylor  and  Navarro. 

EAGLEPOBD  FORMATION 

The  Eagleford  formation  as  developed  in  Bexar  County 
includes  a very  characteristic  series  of  calcareous  and  more  or 
less  sandy  shales.  The  rock  is  granular  in  appearance,  and 
breaks  horizontally  into  thin  slabs,  giving  a flaggy  appearance. 
With  this  light-colored  flaggy  rock  are  found  frequently  layers  of 
much  harder  indurated  clay-lime  rocks.  These  interpolated 
layers  frequently  have  a thickness  of  from  one-half  to  one  foot 
or  more  and  are  probably  continuous  over  considerable  areas. 
The  formation  is  to  some  extent  bituminous  and  when  encoun- 
tered in  drilling  is  frequently  of  a dark  color.  It  also  contains 
sufficient  clay  material  in  parts  of  the  formation  to  cause  the 
tools  to  stick  more  or  less  in  drilling.  For  this  reason  the  forma- 
tion is  sometimes  known  to  the  drillers  as  the  “first  mud”  (the 
Del  Bio  formation  being  the  “second  mud”).  To  most  of  the 
drillers  in  the  central  part  of  Bexar  County  this  formation  is 
known  as  the  “lignite”.  This  name,  although  scarcely  justified 
by  the  characteristics  of  the  formation,  is  firmly  fixfed  in  the 
nomenclature  of  the  drillers  of  this  county.  It  is  not  to  be  con- 
fused, however,  with  the  true  lignite  deposits  which  are  found  in 
much  later  formations  (Tertiary)  not  represented  in  the  central 
and  northern  parts  of  the  county. 

Thickness:  The  Eagleford  formation  is  relatively  thin  in 

Bexar  County.  Practically  all  well  records  place  the  thickness 
of  this  formation  at  from  30  to  35  feet.  In  a few  records  this 
thickness  is  exceeded  slightly,  while  in  others  the  thickness  is 
recorded  as  less,  the  formation  being  recorded  as  absent  in  a few 
wells.  With  regard  to  the  reported  absence  of  the  formation  in 
wells,  it  is  not  impossible  that  occasionally  a well  is  so  located  with 
respect  to  a fault  that  this  formation  is  missed  in  drilling.  Such 
would  be  the  case  if  the  well  were  located  at  a place  where  the 
Austin  formation  is  faulted  against  the  Buda  formation.  On 


Geology  and  Mineral  Resources  of  Bexar  County  35 

the  other  hand,  the  apparent  thinness  and  possibly  the  supposed 
absence  of  the  formation  may  also  be  due  to  local  induration  in 
the  formation  so  that  it  is  not  recognized  in  drilling.  Two  ex- 
posures have  been  found  in  the  county  in  which  it  is  believed 
that  the  full  thickness  of  this  formation  is  shown.  Both  of  these 
exposures  are  on  Salado  Creek  near  the  Blanco  Road  crossing, 
one  below  and  one  above  the  crossing.  In  these  exposures  the 
base  of  the  formation,  resting  upon  the  Buda  limestone,  is  defi- 
nitely limited.  The  top  of  the  Eagleford  where  this  formation 
passes  into  the  Austin  formation  is  much  less  definitely  marked. 
It  appeared  to  the  writer,  however,  that  not  more  than  about  30 
or  35  feet  of  the  exposure  at  these  localities  can  be  referred  to 
the  Eagleford  formation. 

Physiographic  expression:  The  exposures  of  the  Eagleford 

are  scarcely  extensive  enough  to  develop  well  marked  topographic 
features.  However,  as  the  formation  is  softer  and  less  resistant 
than  either  the  Buda  below  or  the  lower  part  of  the  Austin 
above,  the  formation  when  exposed  on  relatively  level  land  is 
usually  represented  by  a slight  although  more  or  less  well- 
marked  valley.  On  steep  hill  slopes  the  rocks  of  this  formation, 
though  in  themselves  characteristic  by  their  lithologic  characters, 
do  not  notably  affect  the  surface  features. 

Common  fossils:  Among  the  characteristic  fossils  which  may 
be  frequently  utilized  in  identifying  the  Eagleford  formation 
are  plant  stems  and  fragments,  fish  scales  and  shark’s  teeth. 
As  developed  in  Bexar  County,  the  formation  is  rather  more 
lacking  in  plant  remains  than  at  some  other  localities.  Fish 
scales  and  teeth  are  occasionally  present,  although  rarely 
abundant.  However,  the  lithologic  characters  of  this  formation 
are  so  distinctive  that  little  or  no  difficulty  will  be  experienced 
in  locating  the  formation  on  surface  exposures.  In  well  drillings 
likewise  the  place  of  the  formation  is  readily  recognized  by  its 
place  between  the  Austin  and  the  Buda  formations. 

Surface  exposures:  As  the  Eagleford  is  the.  thinnest  of  the 
formations  recognized  in  Bexar  County,  the  surface  exposures 
are  correspondingly  limited.  The  belt  of  surface  exposures  of 
this  formation  is  closely  associated  with  the  belt  of  exposures  of 
the  Buda  formation  already  described.  On  the  Bulverde  Road 


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it  is  found  exposed,  as  already  noted,  with  and  just  above  the 
Buda  formation  at  about  13.5  miles  from  San  Antonio.  On  the 
Blanco  Road  are  found  the  exposures  of  the  full  thickness  of 
this  formation  on  Salado  Creek  which  have  previously  been 
mentioned,  and  also  an  exposure  in  the  road  on  the  hill  beyond 
the  creek.  An  isolated  exposure  of  this  formation  is  seen  also 
on  a small  stream  on  the  Lockhill-Selma  Road,  slightly  south  of 
west  of  the  Blanco  Road  crossing  on  Salado  Creek.  On  the 
Fredericksburg  and  Babcock  roads  the  formation  is  first  crossed 
at  about  10  and  11  miles  respectively  from  San  Antonio.  In  the 
western  part  of  the  county  the  formation  is  found  in  a narrow 
belt  too  limited  to  map  except  by  exaggeration.  Exposures  may 
be  seen  on  Canyon  Creek  on  the  Hoffman  Ranch,  within  a few 
miles  of  the  west  boundary  line  of  the  county. 

In  its  sub-surface  position,  the  Eagleford  formation  partakes 
of  the  general  southward  dip,  passing  under  the  later  formations 
The  depth  at  which  it  may  be  expected  from  the  surface  may  be 
deduced  from  the  structural  contour  map  accompanying  this 
report,  on  which  the  actual  level  of  the  top  of  the  Del  Rio  forma- 
tion is  indicated.  The  stratigraphic  interval  from  the  top  of  the 
Del  Rio  to  the  base  of  the  Eagleford  is  about  60  or  65  feet. 

AUSTIN  FORMATION 

The  Austin  formation  includes  a thick  deposit  of  limestone, 
chalk,  and  marl.  The  lower  beds  of  the  formation  are  hard 
limestones.  Higher  up  the  formation  passes  into  a more  chalky 
and  as  a rule  softer  phase,  while  near  the  top  the  deposits  be- 
come chalky  marls.  The  formation  is  stratified  and  consists  in 
places  of  alternating  harder  and  softer  beds,  which  on  weather- 
ing give  a banded  appearance,  in  some  instances  not  entirely  un- 
like that  of  some  exposures  of  the  Glenrose  formation.  On  sur- 
face exposures  the  rocks  of  this  formation  are  prevailingly 
creamy  yellow,  while  in  sub-surface  exposures  the  rock  is  either 
blue,  white,  or  yellow. 

In  drilling,  the  cuttings  from  the  upper  part  of  this  formation, 
including  perhaps  one  or  two  hundred  feet,  as  they  come  to  the 
surface  are  blue  in  color  and  resemble  a clay  or  mud  and  are  in 
some  instances  so  recorded  in  the  drillers * logs.  At  lower 


Geology  and  Mineral  Resources  of  Bexar  County  37 

levels  the  formation  is  white  or  yellow  in  color  and  is  usually 
somewhat  harder  than  near  the  top.  This  phase  of  the  forma- 
tion is  often  referred  to  as  the  “ Magnesian”  rock,  although  so 
far  as  known,  it  is  a calcium  carbonate.  Beneath  the  “ magne- 
sian ” phase  of  the  formation  are  the  harder  limestone  layers  al- 
ready referred  to,  often  described  in  well  logs  as  blue,  gray, 
white,  or  yellow  limestones. 

The  chalk  rock  of  the  Austin  formation  is  used  near  San  An- 
tonio in  the  manufacture  of  portland  cement.  The  harder  lime- 
stones from  the  lower  part  of  the  formation  are  used  for  con- 
crete. The  formation  yeilds  moderate  supplies  of  water,  although 
frequently  containing  more  or  less  hydrogen  sulphide  gas.  The 
oil  of  the  Alta  Vista  and  Mission  fields  is  from  this  formation. 

Thickness:  The  thickness  of  the  Austin  formation  is  difficult 
of  exact  measurement  either  on  surface  exposures  or  from  well 
records.  No  ^locality  has  been  found  in  the  county  where  the 
full  thickness  of  the  formation  can  be  measured  at  the  surface. 
On  the  other  hand,  in  the  well  logs  it  is  extremely  difficult  if  not 
impossible  to  determine  the  level  at  which  the  drill  passes  from 
the  Taylor  to  the  Austin  formation.  The  most  trustworthy 
measurements  of  the  formation  are  those  obtained  from  wells 
known  to  be  located  near  the  contact  line  on  the  surface  of  the 
Austin  and  Taylor  formations  together  with  data  from  >vells 
passing  entirely  through  the  whole  Upper  Cretaceous.  Of  a 
number  of  wells  so  located,  the  following  may  be  cited  as  afford- 
ing the  most  trustworthy  records  available.  The  average  ob- 
tained from  these  wells  indicates  a thickness  of  between  300  and 
400  feet.  The  Government  well  at  the  old  target  range,  now  the 
aviation  post,  on  the  Austin  Road,  6 miles  from  San  Antonio, 
is  probably  located  within  the  belt  of  Taylor  exposures  but  quite 
near  the  Taylor- Austin  contact.  In  the  bed  of  Salado  Creek 
about  one  mile  northeast  of  the  well  and  at  a level  approximately 
75  feet  lower,  is  an  exposure  placed  by  Dr.  Stephenson  as  the 
probable  Taylor-Austin  contact.  Judging  from  the  surface 
exposures  at  the  well  and  from  this  exposure  in  the  stream  bed 
it  is  probable  that  as  much  as  50  or  75  feet  of  the  deposits  at 
the  well  are  to  be  referred  to  the  Taylor  formation.  In  this  well 
the  base  of  the  Austin  was  recognized  at  the  depth  of  353  feet. 


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In  the  log  this  interval  is  divided  up  as  follows:  “Soil,  2 feet; 
yellow  and  blue  clay  and  soft  limestone  or  shale,  218  feet;  and 
chiefly  hard  limestones,  light  gray,  blue-gray,  and  white,  133 
feet”.  On  the  basis  of  the  data  given  above,  it  is  probable  that 
between  275  and  300  feet  of  this  interval  is  to  be  referred  to  the 
Austin  formation,  representing  the  full  thickness  of  the  forma- 
tion at  that  place.  A well  on  the  Waring  estate  near  the  Bandera 
Road,  7%  miles  from  San  Antonio,  is  believed  to  be  located 
within  the  belt  of  surface  exposures  of  the  Austin  formation  or 
with  only  a thin  covering  of  the  Taylor.  In  this  well  there  is 
recorded  beneath  the  surface  soil  and  gravel,  145  feet  of  “blue 
clay”,  and  155  feet  of  yellow,  white,  and  blue  limestones,  giving 
a total  of  300  feet,  all  of  which  with  the  possible  exception  of 
some  clays  near  the  surface  is  to  be  referred  to  the  Austin  forma- 
tion. A well  drilled  at  Schertz  on  the  Cibolo  River  is  also  near 
the  contact  line  of  the  Austin-Taylor1  formations.  A short  dis- 
tance upstream  from  this  well  are  found  surface  exposures  of 
the  Austin  formation,  while  immediately  downstream  are  ex- 
posures of  the  Taylor  formation.  In  this  well  there  are  recorded 
14  feet  of  yellow  clays,  215  feet  of  blue  clay,  and  149  feet  of 
magnesian  and  other  limestones.  This  would  seem  to  indicate 
a possible  thickness  of  378  feet  for  the  Austin.  However,  upon 
other  data  it  is  suspected  that  a fault  or  a very  steep  dip  passes 
immediately  north  of  this  well ; that  is  between  the  well  and  the 
exposures  of  the  Austin  formation.  If  this  is  true,  only  a part 
of  the  229  feet  of  yellow  and  blue  “clays”  of  this  record  is  to  be 
referred  to  the  Austin  formation.  A well  at  the  residence  of 
A.  E.  Goforth  on  the  Culebra  Road,  18  miles  northwest  of  San 
Antonio,  appears  to  be  located  near  the  contact  line  of  the 
Austin-Taylor  formations.  In  this  well  the  base  of  the  Austin 
was  recognized  at  the  depth  of  349  feet,  all  of  which  apparently, 
aside  from  the  surface  materials,  is  to  be  referred  to  the  Austin 
formation. 

From  these  records  it  appears  that  the  Austin  formation  in 
Bexar  County  in  its  belt  of  surface  exposures,  approximates  300 
feet  in  thickness.  From  the  record  of  a considerable  number  of 
wells  drilled  south  of  the  belt  of  surface  exposures  it  appears 
probable  that  the  formation  thickens  toward  the  south.  Among 


Geology  and  Mineral  Resources  of  Bexar  County  39 

the  wells  which  indicate  a thickening  of  the  limestones  southward 
are  the  following : City  water  supply  wells  on  Market  Street  in 
San  Antoino,  hard  rock  above  the  base  of  the  Austin  about  380 
feet;  City  water  supply  'well  near  Conception  Mission  in  south 
San  Antonio,  magnesian  and  other  limestones,  417  feet,  with 
blue  clays  above;  Hoffheintz  well,  southwest  city  limits,  mag- 
nesian and  other  limestones,  exclusive  of  overlying  blue  clay, 
310  feet;  Hill  and  Roby  well,  7 miles  south  of  San  Antonio, 
magnesian  and  other  limestones,  exclusive  of  overlying  clay,  480 
feet.  In  the  Benke  well  on  the  Culebra  Road  near  the  west 
county  line,  limestone  above  the  Eagleford  are  reported  through 
an  interval  of  485  feet,  which  if  referable  in  full  to  the  Austin, 
represents  the  maximum  recorded  thickness  of  the  formation 
in  the  county.  With  due  allowance  for  the  indefinite  record 
afforded  by  the  well  logs,  it  appears  that  the  harder  limestones 
of  this  formation  vary  in  thickness.  In  the  columnar  section  the 
thickness  of  350  feet  is  assigned  to  the  formation,  which  is 
probably  an  average,  being  neither  the  maximum  nor  the  mini- 
mum thickness  in  the  county. 

Physiographic  expression:  The  Austin  formation  appears  on 
surface  exposures  under  two  different  phases  corresponding  to 
the  hard  and  soft  rocks  of  the  formation.  The  limestones  of  the 
lower  part  of  the  formation,  when  exposed,  usually  make  up 
ranges  of  hills  having  a northeast-southwest  trend.  On  these 
hills  the  soils  are  thin  and  contain  considerable  rock  debris.  The 
timber  growth  includes  a preponderance  of  oaks  with  relatively 
little  mesquite.  This  phase  of  the  formation  where  exposed 
usually  forms  a conspicuous  feature  of  the  landscape  and  the 
belt  of  the  hills  may  often  be  seen  and  its  trend  across  the 
county  mapped,  at  a distance  of  some  miles.  The  softer  rocks 
of  the  upper  part  of  the  Austin  formation,  however,  present  on 
surface  exposures  entirely  different  topographic  features.  The 
country  underlying  the  exposures  of  this  part  of  the  formation 
is  usually  gently  rolling  with  rounded  hills  and  gentle  slopes. 
The  native  timber  is  largely  mesquite.  The  soils  are  black  and  at 
the  present  time  the  lands  are  largely  cleared  for  agricultural 
purposes.  This  physiographic  development  corresponds  to  the 
upper  150  or  200  feet  of  the  formation  as  now  delimited. 


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Common  fossils:  The  Austin  formation  is  highly  fossiliferous 
and  a large  number  of  species  of  marine  invertebrates  is  included 
in  the  fauna.  Among  conspicuously  abundant  fossils  of  the 
lower  limestones  of  the  formation  are  the  oysters,  Gryphea 
aucella  and  Exogyra  laeviuscula.  These  fossils  are  particularly 
abundant  in  certain  layers  of  the  limestones  of  the  Austin  forma- 
tion. One  of  the  best  exposures  showing  these  fossils  is  found 
in  the  rock  quarry  near  the  north  side  of  San  Pedro  Park  where 
the  fossil  horizon  includes  a ledge  of  rock  from  one  to  two  feet 
thick,  lying  five  or  six  feet  above  the  base  of  the  exposure.  A 
similar  fossiliferous  ledge  appears  in  the  Ling  Quarry  at  the 
west  side  of  San  Antonio  River  at  the  north  city  limits,  lying 
near  the  base  of  the  exposure.  From  a well  drilled  nearby,  it  is 
known  that  the  base  of  the  Austin  formation  at  this  place  lies 
about  100  feet  below  the  bed  of  the  river,  hence  unless  affected 
by  concealed  faulting  the  horizon  of  these  fossils  at  this  place  is 
between  100  and  125  feet  above  the  base  of  the  formation.  A 
notable  exposure  of  a similar  fossiliferous  bed  of  the  Austin 
formation  is  seen  in  the  bluffs  on  Leon  Creek  near  the  Bandera 
Road  crossing. 

The  upper  beds  of  the  formation  contain  considerable  numbers 
of  the  large  oyster,  Exogyra  ponderosa*  found  also  in  the  Taylor 
formation.  This  oyster  is  believed  not  to  extend  its  range  be- 
low the  softer  beds  of  the  upper  part  of  the  formation,  being 
apparently  absent  from  the  hard  limestones  of  the  lower  beds. 
This  fossil  is  found  in  the  upper  part  of  the  formation  at  many 
localities.  At  the  Bandera  Road  crossing  on  Leon  Creek,  the 
species  seems  to  extend  its  range  downward  to  the  top  of  the 
hard  limestones  of  the  formation  and  to  within  a few  feet  of 
the  level  of  the  Gryphea  bed. 

Surface  exposures  and  local  details:  Surface  exposures  of  the 
Austin  formation  are  found  throughout  a broad  belt  having  a 
northeast-southwest  trend  across  this  county.  The  Austin  belt 
is  somewhat  interrupted  in  part  by  surface  erosion  and  in  part 
by  terrace  deposits,  but  more  especially  by  faulting  and  folding 

*The  Exogyra  of  the  Austin  formation,  according  to  Bose  is 
specifically  distinct  from  E.  ponderosa  of  the  Taylor  formation. 
Univ.  Texas  Bull.,  No.  1902,  1919. 


Geology  and  Mineral  Resources  of  Bexar  County  41 

by  which  other  formations  are  interpolated  into  the  belt  of 
country  otherwise  occupied  chiefly  by  this  formation.  On  the 
line  across  the  Austin  formation  in  the  eastern  part  of  the  county 
marked  by  the  Bulverde  and  Perrin-Beitel  roads,  there  are  two 
distinct  belts  of  Austin.  The  northern  belt  of  Austin  exposures 
is  crossed  on  the  Bulverde  Road  from  1%  miles  north  of  Wet- 
more  to  Wetmore;  the  southern  belt  is  crossed  on  the  Perin- 
Beitel  Road  from  about  1%  miles  south  of  Wetmore  to  Pratt 
station  on  the  Austin  Road. 

On  the  Blanco  Road  extending  due  north  from  San  Antonio, 
are  likewise  found  two  belts  of  the  Austin  formation.  On  this 
road,  however,  the  northern  belt  is  found  to  be  much  wider  than 
on  the  Bulverde  Road,  having  a width  of  about  five  miles.  The 
southern  belt  on  the  other  hand  is  much  narrowed,  having  a 
width  probably  of  scarcely  more  than  a mile.  This  southern 
belt,  as  indicated  in  the  mapping,  passes  below  the  surface  within 
the  city  of  San  Antonio,  giving  place  to  the  Taylor  formation. 
The  broad  belt  of  surface  exposures  of  the  Austin  formation  is 
crossed  on  the  Culebra  Road  from  Leon  Creek  to  about  18% 
miles  from  San  Antonio.  From  surface  exposures  it  is  known 
that  the  Taylor  formation  lies  on  this  road  both  at  the  south- 
eastern and  at  the  southwestern  boundaries  of  the  Austin  ex- 
posures. The  evidence  relating  to  structure  of  these  formations 
is  more  fully  presented  subsequently.  The  high  lands  of  the 
central  part  of  this  belt  present  surface  exposures  that  on  litho- 
logic characters  must  be  placed  as  well  down  in  the  Austin 
formation.  The  Potranca  Road  which  branches  off  from  the 
Culebra  Road  at  the  Leon  Creek  crossing,  and  runs  slightly 
south  of  west,  affords  for  some  miles  exposures  which  are  prob- 
ably near  the  top  of  the  Austin,  many  of  them  containing  an 
abundance  of  Exogyra  ponderosa.  However,  from  about  Medio 
Creek  to  the  county  line,  this  road  in  places  affords  exposures 
including  the  Gryphea  zone  that  are  to  be  referred  to  the  lower 
half  of  the  Austin  formation. 

In  its  sub-surface  position,  this  formation  presents  the  char- 
acteristics of  the  other  formations  of  this  part  of  the  state.  In 
general  the  dip  is  to  the  south  or  southeast.  The  southernmost 
well  in  this  coufity  in  which  the  formation  has  been  definitely 


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University  of  Texas  Bulletin 


recognized,  is  that  on  the  J.  K.  Lamb  property  16  miles  south 
and  2%  miles  east  of  San  Antonio.  At  this  place  the  top  of  the 
formation  lies  approximately  1600  feet  below  the  surface.  To 
the  southeast  the  formation  lies  somewhat  deeper.  From  the 
log  of  the  Bradley  and  Winters  well  at  Saspamco  it  appears  that 
the  formation  at  the  county  line  on  the  Goliad  Road  altho 
not  reached  must  lie  at  least  2500  feet  from  the  surface. 

The  rock  bluffs  and  cliffs  at  the  west  side  of  Brackenridge 
Park  in  San  Antonio  are  composed  of  this  formation  and  afford 
good  exposures  of  the  heavy  limestones.  The  Ling  rock  quarry 
just  across  the  city  limits  at  the  north  side  of  the  park,  is  opened 
up  also  in  the  Austin  formation.  In  a well  drilled  at  the  north 
city  limits  in  Brackenridge  Park,  in  1918,  a log  of  which  is  given 
elsewhere,  the  Eagleford  shales  were  recognized  at  the  depth  of 
101  feet.  It  is  thus  seen  that  the  exposures  iir  Brackenridge 
Park  and  in  the  rock  quarry  north  of  the  park  lie  within  the 
lower  part  of  the  Austin  and  represent  the  formation  from  about 
100  to  140  or  150  feet  above  its  base.  The  rock  as  seen  at  these 
exposures  is  light-colored  or  tinged  with  yellow;  it  is  evenly 
bedded,  consisting  of  layers  from  six  inches  to  several  fe$t  in 
thickness.  Pyrite  nodules  originally  on  the  limestone  have  be- 
come oxidized  and  are  represented  by  spots  or  nodules  of  rusty- 
colored  iron  oxide.  Near  the  base  of  the  section  at  the  quarry  is 
a layer  in  which  a small  Gryphea  is  very  abundant.  At  the  west 
limits  of  Alamo  Heights,  overlooking  the  valley  of  Olmos  Creek, 
there  is  a bluff  into  which  a quarry  has  formerly  been  opened, 
representing  a phase  of  the  Austin  formation  similar  to  that 
seen  in  Brackenridge  Park.  The  Gryphea  layer  at  this  exposure 
lies  45  feet  or  more  above  the  stream  bed,  indicating  that  the 
section  here  affords  an  exposure  lying  a little  lower  in  the  forma- 
tion than  the  exposures  at  Brackenridge  Park.  Immediately 
west  of  the  West  Texas  Military  Academy,  a little  more  than  a 
mile  north  of  the  north  city  limits  of  San  Antonio,  is  another 
west-facing  bluff,  exposing  a similar  section  of  the  Austin  forma- 
tion. The  exposures  of  this  formation  at  the  cement  plant  two 
miles  north  of  the  city  limits  are  described  elsewhere.  At  San 
Pedro  Park  are  seen  exposures  of  the  hard  limestones  of  the 
Austin  formation  from  which  springs  emerge.  The  exposures 


Geology  and  Mineral  Resources  of  Bexar  County  43 

here  described  lie  within  and  represent  an  upthrust  block  of  the 
Austin  formation  which  forms  the  range  of  Austin  Hills  indi- 
cated on  the  sketch  map  (Fig.  2).  The  southernmost  exposure 
seen  of  this  belt  of  Austin  is  found  near  the  intersection  of  Zal- 
zamora  and  Ruiz  streets  in  west  San  Antonio,  where  a much  later 
phase  of  the  formation  is  seen,  consisting  of  soft  marly  rock.  To 
the  northeast,  exposures  of  this  belt  of  the  Austin  formation  may 
be  seen  to  the  county  line  at  the  Austin  Road  crossing  on  the 
Cibolo  River.  Particularly  good  exposures  -are  seen  at  the  cross- 
ing of  the  Austin  Road  on  Salado  Creek,  and  at  the  Perin-Beitel 
Road  crossing  of  a tributary  entering  from  the  east.  On  these 
exposures  Baker  has  made  the  following  notes : 

When  fresh  the  chalk  has  a light  bluish-gray  color  while  on 
weathered  exposures  it  is  light  yellowish-buff,  passing  upward,  upon 
weathering,  to  a brown  substance  resembling  marl.  It  is  much 
jointed  in  very  irregular  fashion  and  breaks  often  with  a semi-con- 
choidal  fracture.  Nodules  of  pyrite  are  present  which  weather  to 
limonite.  Some  beds  of  the  rock  are  slightly  more  indurated  than 
others  and  so  stand  out  more  prominently  on  exposed  surfaces. 
This  rock  forms  the  bed  rock  at  Fratt.  Near  the  mouth  of  the  small 
creek  tributary  to  Salado  Creek  and  heading  northeast  of  Fratt, 
the  dip  (probably  not  true  dip)  is  1°  S 65°  E.  About  one-fourth 
mile  downstream  and  about  200  yards  above  the  junction  with  Sal- 
ado Creek,  the  dip  (perhaps  not  maximum)  is  4°  to  the  south. 

In  the  soft  chalk  rock  of  the  Austin  formation  at  the  crossing 
of  the  Perrin-Beitel  Road  near  Fratt,  Stephenson  has  noted  the 
presence  of  the  following  fossils  (Mss.  notes)  : Scaphites  sp., 
Placenticeras  sp.,  and  a large  Baculites.  In  the  more  indurated 
rocks  of  this  formation  about  one  mile  farther  west,  he  notes 
the  presence  of  the  following  fossils:  Exogyra  laeviuscula, 

Avicula?,  Pecten  sp.,  Liopsifka  elegantula  (Roemer)  ?,  Barbatia 
sp. 

Exposures  in  the  large  belt  of  the  Austin  formation  passing 
through  the  county  north  of  San  Antonio  are  too  numerous  to 
receive  separate  description.  This  belt  of  the  Austin  is  crossed 
by  all  roads  running  north  and  northwest  from  San  Antonio.  At 
the  Leon  Creek  crossing  on  the  Bandera  Road  are  seen  good 
bluffs  exposing  the  hard  limestones  of  the  formation  including  in 
some  layers  an  abundance  of  fossils.  Other  good  bluffs  are  seen 


44 


University  of  Texas  Bulletin 


at  the  first  and  second  crossings  of  the  Culebra  Creek  on  the 
Culebra  Road.  At  the  Salado  Creek  crossing  of  the  Bulverde 
Road,  the  bluffs  seen  at  the  right  are  a part  of  the  limestones 
of  the  Austin  formation  and  represent  the  west  margin  of  the 
block  originating  in  San  Antonio. 

TAYLOR  FORMATION 

The  Taylor  formation  includes  chiefly  marls  and  calcareous 
clays.  In  surface  exposures  and  to  the  depth  affected  by 
weathering,  the  clays  are  yellow,  although  where  unaffected  by 
weathering  they  are  for  the  most  part  blue  in  color. 

As  a water-bearing  formation,  the  Taylor  is  of  but  slight 
importance  as  the  marls  and  clays  are  too  close  in  texture  to 
carry  large  quantities  of  water.  The  bentonite  deposits  of  this 
county  probably  lie  within  the  Taylor  formation.  The  fuller’s 
earth  deposits  are  either  near  the  top  of  this  formation  or  in  the 
next  later  formation,  the  Navarro.  The  gas  of  the  Gas  Ridge 
field  is  probably  from  this  formation,  while  the  oil  of  the  Somer- 
set field  appears  to  be  either  from  this  or  from  the  Navarro 
formation,  or  possibly  in  part  from  the  Midway. 

Thickness : A measurement  of  the  thickness  of  the  Taylor 

formation  is  extremely  difficult.  No  surface  exposures  found  in 
Bexar  County  are  adapted  to  that  purpose  while  in  well  records, 
it  is  difficult  to  determine  from  logs  or  from  cuttings,  the  depth 
at  which  the  formation  is  either  entered  or  passed  through.  In 
the  Terrell  well  six  miles  south  of  San  Antonio  there  was  assigned 
to  this  formation  by  Hill  and  Vaughan*  a thickness  of  about 
400  feet.  In  the  Alta  Vista  oil  Fields  the  combined  thickness 
of  the  Navarro  and  Taylor  formations,  if  present,  apparently 
does  not  exceed  six  or  seven  hundred  feet,  although  here  a part 
of  the  Navarro  may  have  been  removed  by  erosion.**  In  the 
Kearney  test  well  for  oil  south  of  Leon  Creek,  the  combined 
thickness  of  the  Navarro  and  Taylor  formations  may  be  as  much 
as  900  feet.  In  the  columnar  section,  this  formation  has  been 

*Hill,  R.  T.  and  Vaughan,  T.  W.,  18th  Ann.  Rept.  U.  S.  Geol. 
Surv.,  Part  II. 

**Record  of  Elder-Wolf  well. 


Geology  and  Mineral  Resources  of  Bexar  County  45 

assigned  a thickness  of  450  feet  which  may  be  regarded  as  an 
average  thickness  where  the  formation  is  fully  developed. 

In  the  Mathey  well  of  the  Bexar  Petroleum  Company  the  Ter- 
tiary as  noted  subsequently  under  the  discussion  of  the  thickness 
of  the  Midway  formation,  appears  to  extend  to  the  depth  of 
between  1340  and  1402  feet,-  while  the  Austin  formation  accord- 
ing to  the  driller  was  entered  at  1892  feet  and  continued  to  the 
bottom  of  the  well  2025  feet.  If  this  is  true  there  remains  for 
the  Taylor  and  Navarro  formations  at  this  place  a combined 
thickness  of  not  more  than  552  feet.  The  reduced  thickness  of 
these  formations  may  of  course  be  accounted  for  by  possible 
erosion  from  the  top  since  the  Tertiary-Cretaceous  contact  is 
very  probably  an  erosion  unconformity.  Samples  of  cuttings 
from  this  well  from  1938  feet  and  below  submitted  by  the 
driller  and  examined  by  Dr.  J.  A.  Udden  apparently  represent 
the  Austin  formation. 

Bitty  sio  graphic  expression:  Much  of  the  area  underlain  by  the 
Taylor  formation  in  this  county  consists  of  a level  plain  often 
gravel  covered  by  terrace  deposits.  When  subjected  to  stream 
erosion,  the  hills  formed  from  the  Taylor  marls  are  rounded,  with 
moderate  slopes.  The  soils  derived  from  this  formation  are  black 
and  in  wet  weather  very'  sticky.  The  prevailing  timber  growth 
is  mesquite. 

Common  fossils:  The  lower  part  of  the  Taylor  formation 

contains  an  abundance  of  the  large  oyster,  Exogyra  ponderosa , 
which  is  also  present  as  already  noted  in  the  upper  part  of  the 
Austin  formation.  The  Taylor  formation  may  be  separated 
from  the  Austin  probably  within  approximate  limits  upon  litho- 
logic characters,  particularly  by  the  presence  of  an  increased  clay 
ingredient.  From  the  overlying  Navarro  formation  it  may  be 
separated  probably  also  within  approximate  limits. 

Glauconite  is  usually  more  or  less  abundant  in  the  Navarro, 
while  it  is  present  in  much  smaller  quantities,  if  at  all,  in  the 
Taylor. 

The  following  notes  on  the  Taylor  formation  have  been  made 
by  Stephenson  (manuscript  notes)  : — 

Taylor  marl,  consisting  of  weathered  greenish-gray,  calcareous 
clay,  is  poorly  exposed  in  the  west-facing  slope  of  Salado  Creek  at 


46 


University  of  Texas  Bulletin 


the  crossing  of  the  Seguin  Road  about  four  miles  north  by  east  of 
the  post-office  building  at  San  Antonio.  The  thickness  exposed  is 
about  10  feet.  It  is  overlain  by  a Pleistocene  gravel  bed  and  the 
latter  is  overlain  by  sandy  loam.  The  Pleistocene  is  15  or  20  feet 
thick. 

On  the  east-facing  slope  of  Salado  Creek  Valley  about  x one  mile 
above  the  crossing  of  the  Missouri,  Kansas  and  Texas  Railroad,  the 
following  section  is  exposed  along  a private  roadway  or  trail: 

Section 


Feet 


Pleistocene: 

3.  Yellow  sandy  clay  loam  with  lines  of  pebbles 


at  irregular  intervals  . 15 

2.  Bed  of  gravel  with  chiefly  flint  pebbles  and 

cobbles  8 


(Unconformity) 

Cretaceous  (Taylor): 

1.  Gray  calcareous  clay  or  shale  with  a few 

poorly  preserved  fossils 6 

From  the  Taylor  (layer  No.  1)  'obtained  the  following  fossils 
(Collection  No.  182): 

Hamulus  onyx  Morton 
Ostrea  plumbsa  Morton 
Anomia  argentaria  Morton 
Paranomia  sp. 

Pecten  sp.  (small) 

Liopistha  (Cymella)  bella  (Conrad)? 


Bluff  on  Salado  Creek,  left  bank,  3 % miles  due  east  of  Alamo 
Heights,  Bexar  County,  Texas. 


Section 


Feet 


Pleistocene: 

Irregularly  bedded  loam  and  calcareous  sand 
and  gravel.  The  sand  and  gravel  are  ex- 
tremely calcareous  in  places,  consisting 
chiefly  of  a spongy  mass  of  lime.  In 
places  the  chief  matrix  of  the  gravel  is 
spongy  lime.  Frequently  pebbles  are 
noticed  with  concentric  layers  of  lime 

about  them  . .1 20 

(Unconformity) 

Cretaceous  (Taylor): 

Gray  (greenish  gray  to  yellow  where  weath- 
ered) calcareous  shaly  clay  carrying  a 


Geology  and  Mineral  Resources  of  Bexar  County  47 

few  poorly  preserved  fossils.  The  shale 
contains  occasional  seams  of  gypsum.  . . .25 

The  fossils  collected  include: 

Lima  (young  individual) 

Pecten  (small) 

Two  feet  of  relatively  soft  bluish-gray  chalk  is  exposed  in  the 
bed  of  Salado  Creek,  about  a half  mile  above  the  preceding.  The 
following  poorly  preserved  fossils  were  obtained  (Collection  No. 
184) : 

Inoceramus  sp. 

Ostrea  plumosa  Morton 
Placenticeras  sp. 

Crustacean  (fragment) 

This  locality  is  one  mile  below  the  crossing  of  the  Austin  Road. 
The  rock  is  probably  at  the  extreme  top  of  the  Austin  chalk. 

Surface  exposures  and  local  details:  Surface  exposures  of  the 
Taylor  formation  are  found  in  successive  belts  which  extend  in 
a general  northeast  to  southwest  direction  across  the  county. 
Owing  to  structural  features  subsequently  to  be  described,  the 
belts  of  exposures  of  the  Taylor  formation  in  part  surround 
Austin  exposures.  The  northernmost  belt  of  Taylor  is  that 
which  lies  on  the  north  side  of  the  Austin  exposures  on  the 
Culebra  Road.  The  Taylor  in  this  belt  extends  north  to  within 
a mile  or  less  of  the  Balcones  escarpment.  Exposures  represent- 
ing this  formation  may  be  seen  on  the  property  of  H.  Wehmeyer, 
H.  Mossman,  and  R,  Brown,  north  of  the  Culebra  Road.  Ex- 
posures may  be  seen  also  farther  east  on  the  Hoffman  Road  on 
the  property  of  R.  Brown  and  G.  Wehmeyer,  where  the  clays  are 
utilized  in  making  ponds.  At  many  of  these  exposures,  particu- 
larly those  on  the  Brown  and  Wehmeyer  properties,  the  fossil 
Exogyra  ponderosa  is  abundant.  This  belt  of  Taylor  apparently 
terminates  somewhat  east  of  the  Hoffman  Road  at  the  north  turn 
north  of  the  Steubing  cross-road. 

A large  area  of  Taylor  exposures  lies  south  of  the  main  Austin 
exposures.  At  the  west  county  line  these  exposures  are  found 
north  of  the  Castroville  Road,  and  extending  northeast,  lying 
somewhat  south  of,  and  approximately  paralleling  the  Potranca 
Road  to  the  Leon  Creek  crossing.  East  of  Leon  Creek  the  Taylor 
is  seen  on  the  Culebra  Road  at  a cut  in  the  road  8 miles  from 


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University  of  Texas  Bulletin 


San  Antonio.  At  about  this  place,  the  Taylor  belt  is  divided 
by  a southward  projecting  nose  of  Austin  exposures.  On  the 
Fredericksburg  Road,  marls  containing  Exogyra  ponderosa  are 
seen  from  9.3  to  9.7  miles  from  San  Antonio. 

In  the  city  of  San  Antonio,  the  Taylor  exposures  are  again 
divided  by  a southward  projecting  nose  of  the  Austin  formation. 
The  western  area  of  Taylor  marl  is  interpreted  as  crossing  the 
Bandera  and  Fredericksburg  roads  at  from  2.6  to  6.6  and  from 
2.5  to  5.4  respectively  miles  from  San  Antonio.  This  Taylor  belt 
may  be  expected  to  narrow  farther  to  the  east,  and  probably  does 
not  extend  as  far  as  the  east  county  line.  The  oyster,  Exogyra 
ponderosa,  is  found  in  clays  resembling  the  Taylor  on  the  slope 
to  the  alluvial  plain  of  the  Cibolo  on  the  Nacogdoches  road  about 
15  miles  from  San  Antonio. 

In  the  western  part  of  San  Antonio  are  seen  several  exposures 
which  are  referred  more  or  less  definitely  to  the  Taylor  forma- 
tion. One  of  these  is  seen  in  the  cut  on  the  Fredericksburg  road 
at  the  crossing  of  a small  stream  about  two  miles  from  the  Court- 
house. Another  is  seen  at  the  Culebra  Road  crossing  of  the  same 
stream  a little  farther  south.  In  neither  of  these  exposures  are 
fossils  found  and  the  reference  to  the  Taylor  formation  is  on  the 
lithology.  A similar  exposure  of  yellow  clay  is  seen  on  the  same 
creek  still  further  south,  at  the  crossing  of  the  old  Castroville 
Road  near  itg  union  with  Zalzamora  Street. 

The  southernmost  belt  of  Taylor  exposures  in  this  county  is 
that  which  extends  from  San  Anotnio  northeastward  to  the 
county  line.  Exposures  of  the  Taylor  of  this  area  may  be  seen 
at  a cut  in  the  public  road  on  River  Avenue,  at  the  north  city 
limits,  and  again  on  the  Austin  road  opposite  the  Aviation  Post 
about  6 miles  from  San  Antonio.  At  neither  of  these  exposures 
so  far  as  observed  are  fossils  found  and  the  identification  is 
chiefly  on  lithologic  characters.  The  belt  of  the  Taylor  marls 
is  here  narrow  as  the  Austin  formation  is  exposed  a short  dis- 
tance to  the  north,  while  fossils  indicating  the  Navarro  are 
found  not  far  to  the  south  of  these  localities.  To  the  east  of 
Sal  ado  Creek  the  Taylor  formation  lies  south  of  and  approxi- 
mately parallel  to  the  Austin  road,  to  the  county  line. 


Geology  and  Mineral  Resources  of  Bexar  County  49 

NAVARRO  FORMATION 

The  Navarro  formation  includes  chiefly  deposits  of  clay  and 
marl  although  in  parts  of  the  formation,  particularly  toward  the 
upper  limits,  there  are  layers  of  well  indurated  lime  rocks  and 
in  places  limestone  ledges.  Lithologically  the  formation  on  sur- 
face exposures  resembles  the  Taylor.  In  the  Navarro,  however, 
is  found  considerable  glauconite  which  is  frequently  in  such 
abundance  as  to  give  a greenish  tinge  to  the  clays  and  shales  of 
the  formation.  Within  the  formation,  probably  in  its  upper 
part,  is  a green  glauconitic  sandstone,  often  met  with  in  drilling 
and  usually  recorded  in  the  well  logs  as  “green  marl”.  At  the 
surface  exposures  on  Leon  Creek,  this  stratum  has  a thickness  of 
from  12  to  15  feet. 

The  water  supply  in  the  Navarro,  as  in  the  Taylor,  is  very 
limited,  the  marls  and  clays  containing  but  little  water.  The 
greensands  of  the  formation  contain  a limited  amount  of  potash 
and  phosphate,  which  at  the  present  time  is  not  utilized.  The 
oil  of  the  Somerset  field,  as  already  stated,  is  obtained  either 
from  this  formation  or  from  near  the  top  of  the  Taylor  forma- 
tion. 

Thickness:  The  thickness  of  the  Navarro  formation  is  difficult 
to  determine,  since  in  well  logs  and  cuttings  the  transition  from 
this  formation  to  the  underlying  Taylor  is  not  sufficiently  well 
marked  to  be  easily  recognized.  In  a well  on  the  property  of 
J.  K.  Lamb,  south  of  the  Medina  River,  samples  from  which 
were  examined  by  Dr.  J.  A.  Udden,  a thickness  of  about  1000 
feet  was  provisionally  assigned  to  these  two  formations.  On  the 
Ritter  property  on  Medina  River  near  the  Frio  road,  the  strati- 
graphic interval  between  the  top  of  the  Del  Rio  formation  and 
the  uppermost  green  sands  assumed  to  lie  near  the  top  of  the 
Navarro  formation,  is  apparently  between  1250  and  1300  feet. 
Assigning  approximately  400  feet  as  the  combined  thickness  of 
the  Austin,  Eagleford  and  Buda  formations,  there  is  an  indi- 
cated thickness  for  the  Taylor  and  Navarro  formations  of  850 
or  900  feet  at  that  place.  Approximately  the  same  thickness  is 
indicated  by  the  Kearney  well  and  well  of  the  Superior  Oil 
Company.  On  the  basis  of  this  somewhat  indefinite  data,  the 
-I  thickness  of  the  formation  is  given  in  the  columnar  section  at 


4-Bex. 


50 


University  of  Texas  Bulletin 


about  450  feet.  However,  it  is  necessary  to  consider  in  these 
measurements  the  apparently  great  thickness  of  the  Tertiary  in 
the  Mathey  well  and  the  correspondingly  reduced  thickness  of 
the  Navarro-Taylor.  (p.  45.) 

Physiographic  expression:  The  belt  of  country  underlain  by 
the  Navarro  formation  presents  surface  features  not  unlike  those 
of  the  Taylor  marl.  The  slopes  of  the  hills  developed  from  this 
formation  are  possibly  somewhat  more  abrupt  than  are  those 
from  the  Taylor  formation,  due  probably  to  the  presence  of  the 
indurated  limy  layers  of  the  Navarro  formation.  The  soils  are 
black  and  the  prevailing  timber  growth  is  mesquite. 

Common  fossils:  The  Navarro  formation  contains  rather  more 
fossils  than  does  the  Taylor  formation.  The  large  oyster, 
Exogyra  costata , is  abundant  in  this  formation.  Two  other 
oysters,  Gryphea  vesicularis  and  Alectryonia  larva,  are  listed 
by  Hill  and  Vaughan*  as  common  in  this  formation. 

Surface  exposures  and  local  details : The  Navarro  formation 
has  been  recognized  at  surface  exposures  in  a belt  of  country 
passing  across  the  county  from  northeast  to  southwest  imme- 
diately south  of  the  southernmost  belt  of  Taylor  marl.  In  the 
western  part  of  the  county,  this  formation  is  seen  exposed  on 
the  Castroville  Road,  at  the  crossing  of  a small  creek  about  1% 
miles  from  the  county  line  and  again  at  the  top  of  the  hill 
about  2 miles  from  the  county  line.  The  fossil,  Exogyra  costata, 
is  very  abundant  at  each  of  these  exposures.  Another  exposure 
probably  to  be  referred  to  the  Navarro  is  found  near  and 
stratigraphically  above  the  fuller’s  earth  beds  north  of  the  Cas- 
troville Road  17%  miles  from  San  Antonio.  About  one  mile 
south  of  the  Castroville  Road,  on  the  Cagnon  cross  road  14  miles 
from  San  Antonio,  is  an  exposure  on  the  hill  slope  containing 
many  shells  of  E.  costata.  At  the  north  side  of  the  Castroville 
Road,  9 miles  from  San  Antonio,  is  seen  an  exposure  made  by 
an  excavation  for  a pond.  The  yellow  clay  of  this  exposure 
contains  E.  costata.  On  the  Culebra  Read  five  miles  from  San 
Antonio  is  an  exposure  which  is  to  be  referred  either  to  this 
formation  or  to  the  Taylor  marl,  containing  an  abundance  of 
E.  costata.  On  the  Austin  Road  opposite  the  Country  Club 


Austin  Quadrangle,  page  5,  1902. 


Geology  and  Mineral  Resources  of  Bexar  County  51 

grounds  at  the  north  limit  of  the  city  of  San  Antonio  is  an  ex- 
posure -containing  many  E.  costata  which  is  probably  to  be  re- 
ferred to  this  formation.  An  exposure  of  the  Navarro  is  seen 
in  the  cut  made  by  the  Camp  Travis  switch  north  of  the  Seguin 
Road  near  the  east  city  limits  of  San  Antonio. 

A series  of  good  exposures  of  the  Navarro  formation  is  seen 
on  Leon  Creek  from  the  Castroville  to  the  Pearsall  Road  cross- 
ings. About  one-eighth  mile  below  the  Castroville  Road  cross- 
ing on  the  right  bank  of  the  stream  is  a bluff  exposing 
clays  and  limestone  ledges  of  the  Navarro  formation.  The  clays 
on  surface  exposure  are  dun-colored.  A well  dug  nearby,  how- 
ever, shows  that  the  unweathered  clays  are  blue.  The  harder 
ledges  in  this  exposure  are  frequently  concretionary.  The  dip 
as  observed  at  this  exposure,  in  the  direction  about  due  north- 
west, is  about  7 degrees.  About  30  or  35  feet  of  the  formation 
is  seen  at  this  exposure,  overlaid  by  terrace  gravel  deposits.  At 
the  north  side  of  the  Castroville  Road  in  the  right  bank  of  a 
small  tributary  entering  Leon  Creek  from  the  southwest,  about 
one-eighth  mile  from  Leon  Creek,  exposures  are  seen  of  a 
glauconitic  sandstone  horizon.  The  glauconitic  sandstone  at  this 
exposure  dips  rapidly  to  the  northwest. 

In  the  right  bank  of  Leon  Creek  south  of  Kelly  Field,  from 
three-fourths  to  one  mile  above  the  Pearsall  Road  crossing,  is 
a bluff  of  the  Navarro  formation.  The  exposure  here  includes 
70  or  80  feet  of  calcareous  clays  which  are  yellow  on  exposure. 
The  bedding  planes  here  are  obscure,  but  the  dip  in  the  strata 
is  apparently  to  the  northwest.  On  the  left  bank  of  the  stream 
in  Kelly  Field,  an  excavation  made  for  a sewage  disposal  tank 
exposes  thin-bedded  clays,  blue  in  color  or  partially  oxidized 
yellow.  The  dip  as  seen  in  this  pit  in  the  direction 
30  degrees  west  of  south,  amounts  to  about  7 degrees. 
Overlying  the  clays  at  this  exposure  are  the  gravel  terrace 
deposits.  This  exposure  is  interpreted  as  lying  lower  in 
the  Navarro  formation  than  the  exposure  seen  at  the  Castro- 
ville Road  crossing,  the  dip  being  as  noted  to  the  southwest. 
About  one  and  a half  miles  upstream  from  this  exposure  is  a 


52 


University  of  Texas  Bulletin 


bluff  on  the  right  side  of  the  stream.  The  following  section 
is-  seen  near  the  middle  of  this  bluff: — 

Feet 

Heavy  gravel  deposits  at  the  top  of  the  bluff . .16 


Calcareous  clays  weathering  yellow 30 

Glauconitic  sands,  harder  ledges  at  top  and 

base  , . 12 

Dark-colored  clays  30 

Light  marly  white  clays 12 


The  dip  at  this  exposure  is  to  the  west  or  southwest,  amount- 
ing in  places  to  as  much  as  4 degrees.  Near  the  south  end  of 
the  bluff,  the  glauconitic  sandstone  layer  lies  within  about  15 
or  18  feet  of  the  top  of  the  bluff,  or  directly  under  the  gravel 
deposits.  Near  the  north  end,  this  horizon  falls  as  low  as 
about  the  middle  of  the  exposure. 

In  the  bluffs  between  the  Pearsall  and  Quintana  Road 
crossings  are  seen  similar  exposures  of  the  Navarro  formation. 
In  these  exposures,  however,  the  dip  is  in  the  opposite  direction, 
or  to  the  east  or  northeast.  In  this  bluff,  the  glauconitic 
sandstone  comes  into  the  section  near  the  north  end  of  the 
bluff,  where  it  lies  from  90  to  100  feet  above  the  stream.  It 
drops  rapidly  and  passes  below  water-level  somewhat  near 
the  International  and  Great  Northern  Railway  crossing  close 
to  the  Quintana  public  road  crossing.  Baker  has  made  the 
following  notes  on  this  exposure : 

At  the  south  end  of  the  International  and  Great  Northern  Rail- 
way bridge  over  Leon  Creek  is  a blue-gray  unctuous  clay  weather- 
ing yellow-brown,  containing  fossils  and  very  small  streaks  of  sand. 
At  the  south  end  of  the  Southern  Pacific  Railway  bridge,  just  to 
the  west,  glauconitic  sand  containing  small  quartz  pebbles  is  inter- 
bedded  with  sandy  blue-gray  clay.  The  dark  green  glauconitic  sand 
containing  small  pebbles  and  fossils*  notably  sharks’  teeth,  begins 
at  the  railroad  bridges  and  extends  up  Leon  Creek  for  about  a 
mile.  It  dins  15°  to  the  south.  It  probably  represents  the  Na- 
varro formation.  It  is  underlain  by  light  gray  limonite-stained 
sandy  clay.  These  clays  contain  large  gray  sandstone  concretions, 
some  of  which  are  very  well  indurated.  The  clays  weather  tawny 
(yellowish-brown).  The  clays  pass  downward  into  fine-grained, 
thin-bedded,  ripple-marked,  light  gray  sandstone.  A layer  con- 


Geology  and  Mineral  Resources  of  Bexar  County  53 


.taining  many  black  sharks’  teeth  lies  in  the  clay  just  above  the 
sandstone.  The  thin  sandstones  are  interbedded  with  the  clays  and 
the  dip  still  continues.  Lower  down  the  clays  are  darker  in  color 
(greenish  or  olive)  and  are  more  argillaceous  and  unctuous.  The 
dip  flattens  out  northward. 

The  structure  revealed  by  these  exposures  is  interpreted 
as  a broad  asymetrical  anticline  or  tilted  block,  near  the  west 
side  of  which  the  gas  wells  west  of  Leon  Creek  are  located. 
This  structure,  continued  to  the  northeast,  forms  the  Austin 
Hills  elsewhere  described. 

CRETACEOUS-TERTIARY  CONTACT 

The  contact  line  between  the  Cretaceous  and  the  Tertiary  as 
placed  on  the  map  is  at  best  approximate  in  location,  the 
surface  being  much  obscured  by  Pleistocene  gravels.  At  the 
west  margin  of  the  county  the  Tertiary  apparently  extends 
as  indicated  by  sandy  hills  and  occasional  limestone'  concre- 
tions, to  the  slight  bluff  overlooking  the  valley  of  the  Medina 
River.  On  Leon  Creek,  the  Navarro  formation  is  observed  to 
extend  south  as  far  as,  or  somewhat  across,  the  International 
and  Great  Northern  Railway.  At  the  Pearsall  Road  crossing 
on  the  Medina  River,  however,  the  glauconitic  sands  which  are 
provisionally  placed  as  near  the  top  of  the  Navarro  formation, 
are  encountered  in  drilling  at  from  ICO  to  200  feet  below  the 
surface.  Accordingly,  the  eastern  margin  of  the  Cretaceous  in 
this  area  between  the  Medina  and  Leon  Creek  in  which  the 
surface  is  terrace-covered,  is  provisionally  mapped  as  approxi- 
mately paralleling  the  Galveston,  Houston  and  San  Antonio 
Railway.  Between  Leon  Creek  and  the  San  Antonio  River 
the  contact  is  obscured  by  the  Pleistocene  gravels.  Between 
the  San  Antonio  River  and  Salado  Creek  the  Tertiary  repre- 
sented by  the  Midway  formation  extends  north,  reaching  across 
the  southeast  corner  of  the  city  limits  of  San  Antonio.  Be- 
tween Salado  and  Rosillo  Creeks  the  contact  is  again  concealed 
by  the  flood  plain.  On  Rosillo  Creek  .the  Tertiary  extends 
as  far  north  at  least  as  the  St.  Hedwig  Public  Road  crossing  and 
the  Galveston,  Houston  and  San  Antonio  Railway  crossing, 
but  probably  does  not  extend  much  farther  upstream.  Prom 


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University  of  Texas  Bulletin 


here  to  the  east  line  of  the  county,  owing  to  limited  exposures, 
the  contact  is  mapped  approximately  from  the  soil  char- 
acteristics, those  of  the  Tertiary  being  more  sandy  than  the 
soils  derived  from  the  late  Cretaceous  formations. 

CENOZOIC 

EOCENE 

The  Eocene  formations  recognized  in  this  county  are  the 
Midway,  Wilcox,  and  Carrizo,  and  posisibly  outliers  of  the 
Mount  Selman  formation. 

MIDWAY 

The  Midway  formation  of  this  county  includes  chiefly 
arenaceous  clays  in  which  are  imbedded  many  concretions  of 
sandy  or  limy  rocks.  The  concretions  are  of  various  sizes 
from  small  concretions  weighing  only  a few  pounds,  to  those 
of  large  size,  making  up  masses  of  rock  of  several  tons  weight. 

Thickness:  The  most  reliable  measurement  of  the  thickness 

of  the  Midway  formation  obtained  is  that  from  the  Mathey 
well  drilled  in  1919  near  Losoya.  The  following  data  on  this 
well  have  been  kindly  supplied  by  Messrs.  H.  L.  Hamilton  and 
W.  L.  Walker. 


STRATIGRAPHIC  DATA  FORM  MATHEY  WELL 
LOSOYA,  TEXAS 


Horizon. 

Lignite  cuttings  .at  367,  560  and  590  feet.  Wilcox. 

First  fossils  recovered,  from  cuttings,  at  665-670  feet  were: 

*Volutilithes  limopsis  Conrad  Midway. 

Olivella  mediavia  Midway. 

Fossils  found  in  core  sample  from  927  to  928  feet: 

Linthia  alabamensis  Clark  Midway. 

Pecten  alabamensis  Midway. 

Fossil  from  cuttings,  1070-1090  feet: 

Cerithium  mediaviae  Midway. 


Fossils  from  cuttings  at  1110,  1135,  1170,  1195,  1270  and 
1340  feet  all  were  characteristic  Midway  forms  except 
a few  that  carry  through  to  Cretaceous. 

Fossils  from  a core  sample  1402-1406  feet,  were  the  first 
to  definitely  establish  the  Cretaceous: 

Ammonite  * Cretaceous. 

Cuspidaria  Cretaceous. 


*A11  fossil  identifications  were  checked  by  Dr.  J.  P.  Smith. 


Geology  and  Mineral  Resources  of  Bexar  County  55 

The  top  of  the  Midway  horizon  is  somewhere  between  590  and 
665  feet  deep.  The  bottom  is  between  1340  and  1402  feet.  While 
there  is  no  lithological  suggestion  of  lower  contact,  it  would  ap- 
pear that  the  upper  contact  lies  close  to  the  600-foot  level. 

\ 

From  these  determinations  it  appears  that  the  Midway  at 
this  place  has  a thickness  of  between  675  and  810  feet,  and 
that  the  Midway  and  Wilcox  have  a combined  thickness  of 
between  1340  and  1402  feet.  The  record  of  a second  well 
showing  a great  thickness  of  the  Tertiary,  the  Sarah  Smith 
No.  1 of  W.  C’.  Stenbing,  the  data  for  which  has  been  supplied 
by  the  United  States  Geological  Survey,  is  given  in  the  chapter 
on  well  records. 

Physiograhpic  expression : The  belt  of  country  occupied  by 

the  Midway  formation  is  for  the  most  part  moderately  hilly, 
the  hills  having  as  a rule  a southward  slope  which  possibly  in 
many  instances  approximates  a dip  slope.  The  soils  derived 
from  the  formation  are  dark  or  brown  in  color  and  are  more 
sandy  than  are  the  soils  of  the  Cretaceous  although  less  sandy 
than  the  soils  of  the  Wilcox  formation.  The  prevailing  timber 
grown  on  the  Midway  hills  is  mesquite. 

Common  fossils:  Marine  fossils  are  found  in  the  Midway 

although  rarely  abundant.  Of  the  mollusks  the  genus  Veneri- 
cardia  is  the  most  abundantly  represented. 

Surface  exposures  and  local  details:  The  Midway  formation 
is  well  exposed  in  the  cut  made  by  the  Missouri,  Kansas  and 
Texas  Railway  in  the  southeastern  part  of  San  Antonio.  On 
fresh  exposures  the  clays  of  the  Midway  at  this  cut  are  massive, 
much  jointed  and  of  medium  hardness.  On  exposure  they 
crumble  to  very  small  particles.  The  clays  include  numerous 
oval  or  flattened  small  concretions,  frequently  hollow,  or  con- 
taining hematite  or  other  minerals.  Venericardia  was  obtained 
from  this  section  by  Stephenson.  (Mss.  Notes). 

The  following  notes  have  been  made  by  Mr.  Baker,  who  first 
examined  this  exposure  and  recognized  it  as  of  the  Midway 
formation : 

The  Midway  clays  beneath  the  Uvalde  in  the  new  “Katy”  cut 
through  the  hill  in  the  eastern  part  of  San  Antonio  are  not  ap- 
preciably sandy  but  are  more  weathered  than  in  the  lower-lying 
exposures  of  lower  horizons.  This  weathering  was  to  some  extent 


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University  of  Texas  Bulletin 


at  least  accomplished  in  pre-Uvalde  times.  The  clays  are  irregu- 
larly mottled  yellowish-brown  and'  light  olive  green  with  thin  films 
of  dendritic  manganese  oxide  on  joint  planes,  and  an  occasional 
small  white  nodule  or  concretion  of  CaC03.  The  clays  are  much 
jointed. 

Among  other  exposures  of  the  Midway  noted  by  Baker  are 
the  following : 

Greenish  drab  unctuous  clay,  weathering  yellow-brown  with  a 
few  red  limonit'e  sandy  (concretions  and  carrying  Venericardia 
planicosta  and  a few  other  fossils  as  casts,  is  found  in  the  gully 
east  of  ridge  just  below  the  junction  of  Salado  and  Rosilla  creeks. 
In  this  gully  are  seen  also  the  large  yellow  brown  concretions,  some 
of  them  with  cone-in-cone  structure. 

The  Midway  apparently  carries  marine  fossils  to  its  very  top. 
Thus  the  highest  beds  a mile  above  the  mouth  of  Comanche  Creek 
(south  of  Alta  Vista  oil  field)  carrying  the  unctuous  clay  casts  of 
Venericardia  alticostata  and  other  fossils.  As  usual  the  Midway 
here  carries  the  brown  limestone  concretions. 

In  the  Alta  Yista  oil  field  very  large  concretions  are  exposed 
at  the  surface  which  with  little  doubt  are  Tertiary  and  prob- 
ably of  the  Midway  formation.  At  the  crossing*  of  the  Gal- 
veston, Houston  and  San  Antonio  Railway  on  Rosilla  Creek, 
east  of  San  Antonio,  exposures  of  the  Midway  clays  are  seen 
both  in  the  stream  bed  and  in  the  railway  cut.  In  the  dump 
from  dug  wells  near  this  crossing  were  seen  the  massive  clays 
of  this  formation,  including  numerous  small  concretions  identi- 
cal with  those  of  the  Midway  at  the  Missouri,  Kansas  and 
Texas  Railyaw  cut  in  San  Antonio. 

On  the  Miedina  River  exposures  recognized  as  Midway  are 
found  as  far  downstream  as  the  Palo  Alto  Road  crossing.  The 
following  section  at  this  crossing  is  from  notes  made  by  Steph- 
enson : — 


Section  in  ravine  near  north  end  of  bridge  over  Medina  River, 


Palo  Alto  road: 

Feet 

Terrace  deposit: 

1.  Yellowish  sandy  loam  18 

2.  Bed  of  coarse  gravel i 2 

Eocene  (Midway): 


Geology  and  Mineral  Resources  of  Bexar  County 


57 


Hard,  gray,  earthy  sandstone  streaked  with 
reddish  limonitic  iron  ore.  Shows  faint 
cone-in-cone  structure  in  the  more 


earthy  streaks  1 

4.  Dark  gray,  fineiy  sandy,  shaly  clay .18 


5.  Ferruginous  layer  of  fine  earthy  concretion- 
ary sandstone  with  some  concretionary 
masses  of  hard  limestone  in  center. 
Faint  cone-in-cone  structure  noted  in 
the  more  earthy  portions.  A few  faint 
fossil  impressions.  Probably  same  as 
layer  at  bottom  of  bluff  below  Garza 


crossing  1-2 

6.  Dark  gray,  finely  sandy,  shaly  clay 2 

7.  Concealed  to  water  1 5 -(- 


The  lowest  layer  in  the  preceding  section  dips  down  to  water- 
level  within  about  200  yards  below  the  bridge. 

WILCOX  FORMATION 

The  Wilcox  formation  is  well  developed  in  this  county  and 
includes  thinly  laminated  sands,  sandstones,  sand  and  limestone 
concretions,  clays  and  lignites.  The  presence  of  sea  shells  in- 
dicates the  marine  origin  of  parts  of  the  formation,  while  the 
lignite  and  land  plants  preserved  in  some  of  the  shale  indicate 
the  lacustrine  or  near-shore  origin  of  parts  of  the  formation. 

Thickness:  No  data  is  at  hand  at  present  by  which  to  approx- 
imately determine  the  thickness  of  this  formation  in  Bexar 
County.  A well  drilled  near  the  south  county  line  at  Saspamco 
starting  at  or  near  the  top  of  the  Wilcox,  extended  to  a depth 
of  2500  feet.  This  well  with  little  doubt  passes  through  both 
the  Wilcox  and  Midway  and  into  the  Cretaceous,  but  it  is  not 
possible  from  the  log  to  determine  the  limitations  of  the  sev- 
eral formations.  A well  drilled  on  the  J.  K.  Lamb  property  in 
the  southern  part  of  the  county  starts  near  the  top  of  the 
Wilcox.  In  this  well  the  Eagleford  formation,  according  to 
examination  of  the  samples  made  by  Dr.  J.  A.  Udden,  was 
probably  reached  at  about  1900  feet  (Mss.  notes).  Allowing 
for  the  Cretaceous,  overlying  the  Eagleford,  its  usual  thickness 
of  about  1200  or  1300  feet,  there  remain  600  or  700  feet  to  be 
assigned  to  the  Wilcox  and  Midway  formations. 

Physiographic  expression:  The  soils  derived  from  the  Wilcox 
formation  are  sandy  and  frequently  of  a red  color.  The  coun- 


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University  of  Texas  Bulletin 


try  underlain  by  the  formation  becomes  somewhat  hilly  and 
rough  by  the  development  of  stream  channels  and  valleys.  The 
timber  growth  is  mesquite  in  part,  although  deciduous  oaks 
and  other  hardwood  trees  are  found  on  the  more  sandy  lands. 

Common  fossils : The  fossils  of  the  Wilcox  formation  of  this 
county  as  already  indicated  are  in  part  marine  invertebrates 
and  land  plants. 

Surface  exposures  and  local  details : In  the  bluffs  west  of  the 
Pearsall  Road  crossing  on  the  Medina  River  are  numerous 
heavy  limestone  concretions.  The  cut  made  for  the  public  road 
on  this  bluff  exposes  thinly  laminated  sands  carrying  plant 
fragments.  These  sands  and  concretionary  limestones  appear 
to  represent  the  Wilcox  formation.  Similar  laminated  sands 
including  limestone  concretions  are  seen  in  he  bluffs  in  the 
vicinity  of  Van  Ormv.  Good  exposures  of  these  sands  are 
seen  on  the  St.  Anthony  farm  about  three-fourths  of  a mile 
south  of  Van  Ormy.  Sandy  lime  concretions  are  seen  here 
which  measure  as  much  as  35  feet  in  length  by  15  feet  in  width 
and  8 feet  or  more  in  thickness.  They  are  imbedded,  finely- 
laminated,  clayey  sands. 

On  the  Gonzales  Road,  laminated  micaceous  sands  of  the 
Wilcox  formation  are  seen  on  the  slope  to  Saunders  Creek, 
131/2  miles  east  of  San  Antonio  and  thence  in  numerous  ex- 
posures to  the  east  county  line.  At  the  intersection  of  the 
Gonzales  and  Prie  Roads  about  17  miles  from  San  Antonio,  the 
dump  from  a dug  well  was  found  to  contain  typical  sandy 
clays  of  the  Wilcox  formation  including  a few  well  preserved 
leaves.  Thin  lignite  beds  are  reported  in  well  logs  of  this  part 
of  the  county. 

Much  of  the  field  work  on  the  Wilcox  formation  in  Bexar 
County  was  done  by  Mr.  Baker,  from  whose  notes  the  following 
observations  are  taken : 

On  Losoya  Creek,  at  concrete  bridge  on  the  Corpus  Christi  Road, 
the  strata  dip  3°  S 60°  E,  which  may  not  be  the  true  dip.  At  the 
base  of  the  section  are  thin  alternating  beds  of  loose  brown  sands 
and  laminated  clays  overlain  by  brown,  much  cross-bedded  sand- 
stone 3 feet,  above  which  is  mainly  laminated  sandy  clay  about  20 
feet.  The  bottom  of  a small  syncline  is  seen  at  the  bridge,  the  axis 


Geology  and  Mineral  Resources  of  Bexar  County  59 

of  which  trends  northeast-southwest.  The  dip  on  the  northwest 
limb  runs  up  to  10°  or  more,  but  flattens  rapidly. 

A splendid  section  of  the  Wilcox  is  exposed  at  the  jog  in  the 
public  road  about  three  miles  north  of  Elmendorf.  The  section  is 
as  follows: 


Brownish  stained  sands,  weathering  into 

“bad  lands”  8 

Laminated  gray,  medium-grained  sands, 
weathering  light  brown  with  some  thin 
interlaminae  of  yellow-brown  clay 15 


Gray  drab,  unctuous,  structureless  fire 
clay,  passing  downward  into  chocolate 
carbonaceous  shale  and  finally  into  a 
good  grade  of  lignite.  The  lignite  has 
a minimum  thickness  of  2 feet  with  the 


base  not  exposed  6 

Slightly  laminated  brownish-gray  medium- 
grained micaceous  sand  with  large  flat- 
tened elliptical  sandstone  concretions 
at  top  and  bottom  10 


The  observed  dip  in  a direction  about  20°  south  of  east,  ap- 
peared to  be  7°,  but  flattened  out  toward  the  south. 

The  lower  Wilcox  on  Medina  River  at  southern  boundary  of  San 
Antonio  topographic  sheet,  west-southwest  of  Earle,  consists  of 
medium-grained  gray  cross-bedded  sands,  with  large  sandstone  con- 
cretions, weathering  brown.  In  the  bed  of  Comanche  Creek  a short 
distance  above  its  junction  with  Leon  Creek  are  many  very  large 
flattened  sandstone  concretions.  Associated  with  these  are  inter- 
bedded  brown  sands  and  shaly  gray  sandy  clay.  The  lower  Wilcox 
at  the  bridge  over  Six  Mile  Creek,  where  crossed  by  old  Espada 
Mission  ditch,  is  medium-grained  gray  sandstone,  somewhat  cross- 
bedded,  weathering  brown  and  locally  cemented  into  sandstone. 

Near  mouth  of  first  tributary  on  the  west  side  of  Calaveras  Creek 
south  of  crossing  of  road  running  east-northeast  of  Elmendorf,  are 
black  and  brown  layers  carrying  carbonaceous  materials  in  brown- 
ish laminated  sands,  with  alum  incrustations.  Most  of  the  10-foot 
section  is  fine  sand,  some  layers  with  an  admixture  of  clay.  The 
apparent  dip  here,  possibly  due  to  slumping,  is  about  5°  to  the  east. 
Large  ripple-marked  flat  blocks  of  brown  sandstone  occur  in  Cal- 
averas Creek  bed  in  this  locality.  The  sands  are  laminated  and 
when  fresh  are  light  gray  in  color  but  are  often  stained  with 
limonite.  The  Wilcox  soils  are  light  brick  red  and  generally  sandy. 
The  sandstone  layers  in  the  Wilcox  here  are  often  cross-bedded  and 
ripple-marked.  When  fresh,  the  sandstone  is  gray  in  color,  but 
oxidation  of  the  iron  gives  the  brown  most  generally  seen.  Locally 


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University  of  Texas  Bulletin 


they  may  be  almost  as  hard  as  quartzite  but  they  seem  to  be 
almost,  if  not  quite,  always  local  indurations'  of  a concretionary 
nature.  At  one  place  on  Calaveras  Creek  about  half  a mile  below 
the  bridge  before  noted,  ripple-marked  and  cross-bedded  sandstone 
about  3 feet  in  thickness  overlies  large  flattish  concretionary  masses 
cementing  a conglomerate  of  light  brown  clay  balls.  Some  have 
septarian  structure  and  are  seamed  with  crystalline  calcite  and 
cone-in-cone  structure.  These  concretions  contain  marine  Eocene 
fossils,  carbonaceous  fragments  and  grains  of  glauconite.  In  all 
respects  they  resemble  the  Wilcox  concretions  in  Sabine-town  bluff, 
this  being  the  first  locality  of  marine  Wilcox  found  west  of  the 
Sabine  basin.  The  concretionary  layer  is  only  about  4 feet  above 
the  bed  of  the  creek.  Below  are  4 to  5 feet  of  loose  laminated 
sands  and  above  the  sandstone  layer  overlying  the  concretions  are 
about  20  feet  of  laminated  gray  clayey  sands,  limonite-stained  and 
locally  cemented.  The  latter  are  found  in  the  bluff  about  200  feet 
to  the  westward.  The  sandstone  blocks  between  here  and  the 
bridge  evidently  belong  to  the  same  stratum,  the  one  over  the 
fossil-bearing  concretions,  only  one  large  fossiliferous  concretion 
being  known  to  occur  here. 

Nearly  half  a mile  farther  down  is  another  20  foot  exposure  of 
Wilcox.  Here  is  about  5 feet  of  lavender  carbonaceous  sandy  and 
unctuous  clays  at  base,  succeeded  by  cross-bedded,  laminated  sands 
with  occasional  thin  laminae  of  clayey  material  for  the  next  10 
feet.  The  upper  five  feet  consists  of  two  one-foot  beds  of  gray  clayey 
laminated  sands  separated  and  overlain  by  cross-bedded  brown 
sands,  the  upper  2 feet  of  which  is  more  consolidated  and  consists 
of  a conglomeratic  sandstone  with  small  clay-iron-stone  pebbles  and 
small  sharks’  teeth.  This  sandstone  is  also  ripple-marked.  Peb- 
bles of  clay-iron-stone  in  such  a formation  mean  little,  for  they 
are  soon  formed  in  consolidated  condition  along  stream  banks  and 
ocean  or  lake  littoral  deposits. 

From  this  point  on  downstream  to  below  the  steel  wagon  bridge 
at  Saspamco  the  banks  sometimes  30  feet  high  are  composed  of 
alluvium  of  clayey  sand. 

The  first  section  on  Parita  Creek,  V2  mile  above  mouth,  shows  at 
base  6 feet  of  lavender,  carbonaceous,  cross-bedded,  laminated, 
sandy  clay,  dipping  upstream  at  an  angle  of  about  10°,  succeeded 
above  by  about  6 feet  of  laminated  sand  and  being  nearly  horizon- 
tal. The  whole  section  is  prevailingly  sandy,  with  indurated  sand- 
stone layers  both  above  and  below. 

The  first  exposure  on  Parita  Creek  south  of  the  bridge,  about 
4 miles  northeast  of  Elmendorf  (about  1-5  mile  south  of  bridge) 
shows  9 feet  of  thinly  interlaminated  clay  and  sand  layers.  The 
sand  layers  are  generally  thicker  than  the  clay  layers,  but  few  of 
the  former  are  much  thicker  than  an  inch.  The  sand  is  brown, 
weathering  gray  when  fresh.  The  clay  laminae  are  gray  when  dry 


Geology  and  Mineral  Resources  of  Bexar  County  61 

and  lavender  or  light  chocolate  when  wet.  Sand  is  fine-grained 
and  micaceous  and  some  layers  are  2 to  3 inches  thick.  The  next 
three  exposures  downstream  show  substantially  the  same.  The  in- 
terbedding of  sand  and  clay  laminae  still  continues.  Either  one 
may  sometimes  be  extremely  thin,  sometimes  not  much  thicker  than 
bristol  board  or  thin  cardboard.  Light  exposure  about  1 mile  be- 
low bridge  shows  above  10  feet  of  laminated,  brown,  fine-grained 
sands,  with  nodules  arranged  in  thin  layers  of  a whitish  powdery 
substance,  probably  CaC03.  Below  is  10  feet  of  mainly  light  gray, 
thinly-laminated,  sandy  clay  but  containing  one  21/z"  layer  of  sand 
2 y2  feet  above  base.  The  clay  member  has  three  interlaminae  of 
sand  as  was  noted  farther  upstream.  This  exposure  at  junction  of 
east  tributary.  One-half  mile  downstream  below  last  3 feet  of 
rusty  brown  ripple  and  rill-marked  irregular-bedded  sandstone  over- 
lies  unconsolidated  sands  with  interbedded  laminae  of  clay.  The 
next  exposure  downstream  shows  a good  deal  of  cone-in-cone  struc- 
ture in  brown  sandstone  concretionary  layers,  interbedded  with 
clayey  sands. 

On  Calaveras  Creek,  about  2 y2  miles  northeast  of  Elmendorf,  and 
of  Parita  Creek,  near  the  Bexar-Wilson  county  line,  about  y2  mile 
north  of  southermost  of  two  main  road  crossings  in  a northeasterly 
direction  from  Elmendorf,  is  exposed  about  10  feet  of  light  brown 
laminated  sands.  Next  exposure,  a mile  farther  upstream,  has  the 
usual  interlaminated  sands  and  clays  with  flattish  sandstone  con- 
cretions and  selenite  crystals  10  feet  thick.  Also  a 7-foot  exposure 
of  the  latter  on  road  just  east  of  bridge  over  Calaveras  Creek  3 
miles  northeast  of  Elmendorf. 

The  first  exposure  of  any  moment  on  the  largest  eastern  tributary 
of  Parita  Creek,  near  the  Bexar-Wilson  county  line,  about  y2  mile 
above  mouth  of  creek,  consists  of  about  5 feet  of  thinly-laminated 
light  chocolate  clay,  with  very  thin  partings  of  light  gray  mica- 
ceous sand;  above  is  7 feet  of  thinly-laminated  light  gray  clayey 
sand,  seamed  with  limonite,  and  becoming  sandier  and  less  lami- 
nated in  the  upper  2 y2  feet;  capped  by  8 feet  of  light  gray,  fine- 
grained sand  weathering  light  brown  with  thin  beds,  especially  at 
the  top,  of  a white  kaolin-appearing  substance.  The  basal  clays 
contain  carbonaceous  remains.  The  next  exposure,  at  least  3/4 
mile  farther  upstream,  consists  of  the  same  sort  of  materials  as  the 
last  and  a recent  well  dug  in  the  creek  bed  between  the  two  shows 
about  10  feet  of  gray  micaceous  sandy  clays  and  clayey  sands. 
Under  the  last  exposure  noted  lie  brown  concretionary  sandstones 
some  with  cone-in-cone  structure.  These  concretionary  layers,  as 
usual,  are  ripple-marked.  Some  of  them  are  large  flattened  discs, 
gray  in  color  when  fresh,  and  hard  as  quartzite.  The  concretionary 
layers  are  interbedded  with  the  usual  clayey  sands,  which  are  lami- 
nated. Some  of  its  larger  concretions  are  probably  cemented  with 
sphaero-siderite.  A conglomeratic  concretionary  layer,  found  at  least 


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University  of  Texas  Bulletin 


1 y2  miles  upstream  from  the  mouth  of  the  largest  eastern  tribu- 
tary of  Parita  Creek,  was  composed  of  rolled  iron-stone  pebbles, 
shark’s  teeth  and  oyster  fragments.  The  latter  may  have  come  from 
the  Cretaceous.  Also  worn  fragments  of  other  shells. 

As  one  goes  upstream  and  consequently  into  lower  strata,  the 
beds  become  more  clayey,  ^becoming  gray  drab  stained  with  oxide 
of  manganese,  and  with  small  whitish  soft,  perhaps  calcareous 
concretions. 

The  following1  notes  on  the  Wilcox  and  other  Cenozoic  for- 
mations in  Bexar  County  have  been  contributed  by  Dr.  L.  W. 
Stephenson : 

Medina  River,  a few  hundred  yards  below  the  crossing  of  the 
Corpus  Christi  Road  near  Losoya,  Bexar  County,  Texas,  13%  miles 
south  of  the  San  Antonio  postoffice  building. 


Pleistocene: 

2.  Massive  brown  loam,  becoming  sandy  and 
pebbly  toward  base  and  locally  a basal 
bed  of  gravel  reaching  3 or  4 feet  in 
thickness.  The  material  stands  up  in  a 
vertical  wall  along  the  bluff  like  loess.  20-35 
(Profound  unconformity) 

Eocene  (Wilcox?): 

1.  Gray  to  greenish  gray,  cross-bedded  sand 
and  sandstone.  The  sandstone  consti- 
tutes local  indurations  of  the  sand.  It 
is  soft  to  very  hard  and  is  poorly  ex- 
posed along  the  base  of  the  bluff  which 
is  covered  with  talus 15-30 

Faint  banding  is  noticeable  in  layer  No.  2,  and  about  10  feet 
below  the  top  is  a distinctly  lighter  band  having  a yellowish  color. 
The  bluff  extends  for.  several  hundred  yards  along  the  left  bank. 

Earle,  Texas,  11%  miles  due  south  of  the  San  Antonio  postoffice 
building.  At  the  head  of  a gully  on  the  east  side  of  the  road  and 
south  of  Medina  River,  sandstone  has  been  quarried  for  use  in 
concrete  work  at  the  new  bridge  at  Earle. 

The  rock  is  the  indurated  portion  of  a greenish  gray,  cross- 
bedded,  rather  fine  sand  formation.  It  is  not  very  well  exposed, 
the  slopes  being  covered  with  vegetation  and  rock  debris.  Unin- 
durated portions  of  the  sand  are  exposed  in  the  head  of  the  gully 
proper.  Thirty-five  or  forty  feet  of  the  rock  and  the  unconsolidated 


Geology  and  Mineral  Resources  of  Bexar  County  63 

sand  is  exposed.  The  rock  rises  nearly  to  the  surface  of  the  sur- 
rounding upland. 

Down  the  gully  the  rock  and  sand  are  overlain  by  Pleistocene 
sandy  loam  which  rests  unconformably  against  it.  The  sandstone 
contains  large  numbers  of  fossil  leaves  well  preserved.  As  the 
rock  does  not  split  well  the  leaves  are  hard  to  get  out  in  perfect 
condition.  (Collection  No.  181).  I was  informed  of  the  where- 
abouts of  the  fossil  plant  locality  just  described  by  Mr.  T.  B.  Apple- 
white,  whose  address  is  R.  F.  D.  No.  7,  Box  33,  San  Antonio,  Texas. 
(The  fossil  leaves  from  this  locality  have  been  described  by  E.  W. 
Berry  in  Prof.  Paper  91,  pp.  8-20,  pis.  1-3,  1916). 


Corpus  Christi  Road,  crossing  of  Losoya  Creek,  half  a mile  south 
tff  Medina  River  crossing. 

Section 

Feet 


Surficial-alluvium : 

Reddish  brown  sandy  loam  with  accumula- 
tion of  pebbles  at  base  in  places.  Con- 
tains land  shells '. 4-15 

(Great  unconformity) 

Eocene  (Wilcox?): 

Laminated,  finely  sandy,  gray  clay,  and  part- 
ings and  thin  layers  of  gray  to  brown- 
ish fine  sand,  some  layers  6 or  8 inches 
thick.  Some  vegetable  particles.  Max..  20 

Layer  of  ferruginous  earthy  sandy  lime- 
stone, apparently  of  concretionary 
origin,  cemented,  on  top  of  which  is  a 
thin  conglomeratic  layer  composed  of 
coarse  pebbles,  most  of  which  appear  to 
be  fine  ferruginous  sandstone  and 
sandy  iron  carbonate  concretions. 
Among  those  pebbles  were  collected  a 
few  poor  prints  of  Venericardia.  Also 


some  silicified  wood 1 

Irregularly  bedded  sandstone  and  loose 
sand,  some  showing  ripple  marks,  with 
subordinate  gray  laminated  clay 4 


CARRIZO  FORMATION 


The  Carrizo  sandstone  was  named  and  described  by  Owen  in 
the  First  Report  of  Progress  of  the  Texas  Geological  Survey, 
published  in  1889.  The  Carrizo  formation  of  the  Cambrian 
system  exposed  in  the  Carrizo  Mountains  of  the  Van  Horn 


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University  of  Texas  Bulletin 


Quadrangle,  was  named  by  Yon  Streeruwitz  in  1891. # If,  there- 
fore, the  Carrizo  of  the  Eocene  is  recognized  as  of  formation 
rank,  the  name  as  applied  to  this  sandstone  takes  precedence 
over  the  Carrizo  formation  of  the  Cambrian.  The  Queen  City 
member  of  the  Wilcox  formation,  which  is  usually  regarded  as 
the  northeast  Texas  equivalent  of  the  Carrizo  sandstone,  was 
named  by  Kennedy  in  1896. f The  Carrizo  sandstone  is  re- 
garded by  some  as  a member  of  the  Wilcox  formation. 

A belt  of  sand  hills  extends  across  the  southernmost  part  of 
Bexar  County,  representing  country  underlain  either  by  the 
Carrizo  sandstone  or  by  very  sandy  phases  of  the  Wilcox.  This 
area  is  referred  to  locally  as  the  ‘ ‘ sand  hills  ’ ’.  The  approximate 
location  of  this  belt  of  country  is  indicated  on  the  map. 

Some  of  the  hills  near  the  county  line  in  the  southwestern 
part  of  the  county,  thickly  strewn  with  concretionary  ironstone 
fragments,  may  represent  outliers  from  the  Mt.  Selman  forma- 
tion. 

PLEISTOCENE 

No  marine  formations  are  found  in  this  county  of  later  date 
than  the  Eocene  period,  the  late  Cenozoic  being  represented  only 
by  non-marine  deposits,  including  river  flood-plain,  and  to  some 
extent  chemically  formed,  sediments.  Presumably,  as  indicated 
by  the  absence  of  marine  formation,  this  area  has  been  subjected 
to  surface  erosion  during  the  latter  part  of  the  Tertiary  and  all 
of  the  Pleistocene.  In  this  long  interval  there  has  been  formed 
a complicated  and  extensive  series  of  river  flood  plains.  The 
earliest  or  oldest  of  these  have  themselves  been  more  or  less  com- 
pletely destroyed  and  removed  by  erosion.  Of  those  that  remain 
some  are  as  old  as  the  early  Pleistocene,  or  possibly  older,  while 
others  were  formed  during  the  middle  and  latter  part  of  the 
Pleistocene  period. 

For  a part  only  of  this  county  are  topographic  maps  available, 
and  it  has  not  been  practicable  to  make  a .detailed  study  of  the 
successive  flood  plains.  It  is  important,  however,  to  indicate 

*Second  Annual  report  of  the  Geol.  Surv.  of  Texas,  p.  683,  1890. 

fThe  Eocene  Tertiary  of  Texas  east  of  the  Brazos  River.  By 
Wm.  Kennedy.  Proc.  Acad.  Nat.  Sci.  Phila.  for  1895,  p.  135,  1896. 


Geology  and  Mineral  Resources  of  Bexar  County  65 

the  general  characteristics  of  the  flood  plain  deposits,  and  to 
map  the  larger  areas. 

The  flood-plain  deposits  of  the  county  may  be  divided  into  two 
main  groups,  each  of  which  is  distinctive.  The  first  of  these 
groups  includes  the  older  and  hence  higher  terraces  of  the  county 
which  are  not  obviously  associated  with  the  existing  streams. 
The  second  group  includes  the  low  or  late  terraces  whose  rela- 
tion to  existing  streams  is  sufficiently  evident.  Data  on  which  to 
determine  the  age  of  the  older  terraces  are  wanting,  but  they 
may  safely  be  placed  as  early  Pleistocene  or  older.  The  late 
terraces  are  recognized  as  belonging  to  the  latter  part  of  the 
Pleistocene  period. 

The  older  and  higher  flood-plains,  of  which  there  are  at  least 
two  and  probably  several,  have  some  characteristics  in  common. 
As  already  stated  they  are  not  obviously  associated  with  the 
existing  streams.  The  sediments  of  these  older  terraces  are 
locally  more  or  less  firmly  cemented  by  calcium  carbonate  thus 
differing  from  the  materials  of  the  recent  terraces,  which  are 
largely  uncemented.  Paleontologically,  the  older  terraces  pre- 
sent the  negative  characters  of  a complete  or  almost  complete 
absence  of  fossils,  while  the  more  recent  terraces  contain  fresh 
water  land  snails  and  in  places  vertebrate  remains.  Concretion- 
ary or  pisolitic  calcium  carbonate  pebbles  subsequently  more 
fully  described,  are  occasionally  found  in  the  older  flood-plains 
and  in  places  are  abundant,  making  up  locally  the  greater  part 
or  all  of  the  formation. 

UVALDE  FORMATION  AND  UVALDE  PLAIN 

(Pliocene  or  Pleistocene) 

The  oldest  and  highest  flood  plain  deposits  of  this  area  are 
probably  contemporaneous  in  age  with  those  which  have  else- 
where been  referred  to  the  Uvalde  formation.  The  materials  of 
this  formation  as  developed  in  Bexar  County  include  limestone 
and  flint  boulders  often  imbedded  in  a softer  matrix  of  finer 
material,  clay  or  silt,  or  in  some  instances  soft  calcareous  ma- 
terial resembling  caliche.  Approaching  the  Balcones  Escarp- 
ment, the  limestone  boulders,  as  would  be  expected,  increase  both 
in  relative  abundance  and  in  size.  Southward  from  this  escarp- 


5-Bex. 


66 


University  of  Texas  Bulletin 


raent  the  relative  amount  of  flint  pebbles,  although  of  smaller 
size,  are  in  proportionately  greater  abundance.  The  flints  of 
this  formation  were  derived  largely  from  the  Edwards  forma- 
tion The  limestone  boulders  came  originally  from  this  or  from 
other  limestone  formations,  having  been  moved  in  many  in- 
stances probably  no  great  distance.  Well  to  the  south  where 
this  flood  plain  overlies  Upper  Cretaceous  formations,  there  are 
undoubtedly  extensive  inclusions  from  these  formations.  Un- 
der these  conditions  the  Uvalde  may  contain  beds  of  clay  and 
marly  deposits  which  are  with  difficulty  separated  from  the  im- 
mediately underlying  Upper  Cretaceous  formations.  Many  of 
the  flint  pebbles  of  this  formation  are  coated  with  calcium  car- 
bonate. The  amount  of  this  coating  varies  from  mere  films 
surrounding  large  flints  to  calcium  carbonate  concretions  oi 
varying  sizes  around  fragments  of  flints  as  a nucleus.  These 
concretions  are  more  fully  described  subsequently.  The  gradient 
of  the  streams  being  reduced  in  passing  coastward  from  the  hills, 
the  coarse  materials  o'f  all  these  flood  plains  grade  to  fine  silts 
and  loams  which  are  non-resistant  to  erosion  and  are  finally  lost. 

The  gravels  of  the  Uvalde  formation  are  utilized  in  road 
building  and  for  concrete. 

Thickness:  The  Uvalde  plain,  being  the  oldest  of  the  flood 

plains  of  this  area,  has  been  cut  into  and  largely  destroyed  by 
erosion,  and  hence  persists  as  hardly  more  than  a remnant  of 
its  former  extent.  In  thickness  the  formation  probably  varied 
greatly  depending  upon  the  irregularities  of  the  top  surface  of 
the  underlying  formations.  In  those  areas  where  the  formation 
now  persists  there  is  observed  a thickness  varying  from  a few 
feet  to  as  much  probably  as  70  feet,  although  more  commonly  the 
gravels  of  this  formation  are  between  15  and  30  feet  in  thickness. 

Surface  exposures  and  local  details:  Originally  the  Uvalde 

flood  plain  must  have  occupied  an  extensive  area  immediately 
south  of  the  Balcones  Escarpment,  grading  from  very  coarse 
materials  near  the  hills  to  silts  and  loams  farther  south.  The 
softer  materials  of  the  formation  probably  were  first  removed  by 
erosion,  the  gravels  and  heavy  conglomerates  having  been  more 
persistent.  Some  of  the  areas  occupied  by  this  formation  are 
indicated  on  the  map,  although  for  reasons  elsewhere  stated  it  has 


Geology  and  Mineral  Resources  of  Bexar  County  67 

not  been  possible  to  represent  all  of  the  flood  plains  deposits  of 
the  county. 

The  range  of  Austin  Hills  crossed  on  the  Fredericksburg 
Road  eight  miles  from  San  Antonio  are  overlaid  by  a remnant 
of  the  Uvalde  formation.  The  formation  is  well  exposed  on  this 
road  7.8  miles  from  San  Antonio,  where  it  consists  of  flint  and 
hard  limestone  gravel  imbedded  in  a chalky  matrix.  In  a cut 
on  the  Altgelt-Wurtzbach  road  near  its  union  with  the  Fred- 
ericksburg Road,  8.7  miles  from  San  Antonio,  is  another  good 
exposure  of  the  formation.  The  lower  part  of  the  exposure  here 
is  chiefly  very  soft  white  marly  material  overlain  by  about  eight 
feet  of  gravel  including  some  very  heavy  limestone  boulders. 
This  area  of  the  Uvalde  formation  continues  with  some  interrup- 
tions as  far  to  the  southeast  as  the  Waring  estate  between  the 
Bandera  and  Culebra  roads.  The  elevation  of  these  exposures 
varies  from  about  1010  feet  at  the  Fredericksburg  Road  crossing 
to  850  or  900  feet  at  the  Waring  estate. 

No  fossils  are  known  from  the  Uvalde  gravels  except  possibly 
some  invertebrates  that  have  washed  into  the  formation  from 
the  older  formations. 

Physiographic  expression : The  Uvalde  formation  makes  a 
plain  now  much  cut  into  by  erosion.  The  slope  of  this  plain  is 
more  pronounced  than  that  of  the  next  later  plain.  Thus  the 
Uvalde  plain,  if  correctly  identified,  slopes  south  at  the  rate  of 
about  20  feet  per  mile,  while  the  lower  plain  on  which  Kelly 
field  is  located,  slopes  south  at  about  15  feet  per  mile.  Locally 
the  materials  of  this  formation  have  become  firmly  cemented 
forming  hard  calcareous  rocks.  Under  these  conditions  rocky 
thin  soils  are  found,  clothed  with  a mixed  vegetation,  chiefly 
oaks ; more  commonly,  especially  toward  the  southern  part  of  the 
area,  occupied  by  the  formation,  the  soils  are  very  gravelly  and 
the  prevailing  timber  growth  is  mesquite. 

Surface  exposures  and  local  details:  On  the  west  side  of  Leon 
Creek  west  of  San  Antonio  is  found  a considerable  remnant  of 
a flood  plain  which  may  be  either  an  extension  of  the  Uvalde 
plain  or  probably  may  be  a plain  at  a slightly  lower  level.  The 
plain  here  lies  at  the  Castroville  road  crossing  at  an  elevation 
of  from  750  to  800  feet  above  sea  level.  To  the  south  this  plain 


68 


University  of  Texas  Bulletin 


may  be  recognized  to  about  the  Frio  Road  crossing  where  it 
terminates  by  surface  erosion  although  probably  remnants  may 
be  found  somewhat  farther  south.  The  plain  may  be  traced  to 
the  north  where  it  seems  to  pass  without  any  very  appreciable 
break  onto  the  plain  adjacent  to  Culebra  Creek.  On  the  up- 
lands between  Medio  and  Potranca  creeks  are  terrace  plain  rem- 
nants which  apparently  lie  at  about  the  same  level,  and  origi- 
nally perhaps  were  parts  of  the  same  plain. 

At  the  north  side  of  the  Castroville  Road,  about  one-fourth 
mile  beyond  Leon  Creek,  deep  gullies  have  washed  into  the 
gravel  beds  of  this  plain,  affording  a good  exposure.  The 
formation  here  rests  on  the  Navarro  and  the  lower  three  feet 
in  this  exposure  consists  of  a very  heavy  pebble  conglomerate 
in  which  are  found  large  masses  of  glauconitic  sandstone  de- 
rived from  the  Navarro  formation.  These  green  sandstones 
of  the  Navarro  are  now  exposed  as  elsewhere  noted  in  the 
same  bluff.  Above  this  level  is  seen  white  marly  material. 
Near  the  top  of  the  exposure  pebble  beds  again  come  into  the 
section. 

An  exposure  of  gravel  which  is  probably  to  be  referred  to 
the  Uvalde  formation  is  seen  in  a cut  in  the  public  road  on  New 
Braunfels  Avenue,  about  0.7  mile  north  of  the  north  city  limits 
of  San  Antonio.  In  this  cut  there  are  exposed  about  ten  feet 
of  clay,  white  chalky  marl,  and  gravel.  The  gravel  beds  are 
strongly  cross-bedded.  The  clay  of  this  exposure,  although 
probably  included  within  the  gravel  series,  closely  resembles 
the  clay  of  the  Taylor  formation  which  is  exposed  on  River 
Avenue  nearby.  Similar  gravel  beds  underlie  the  high  lands 
north  and  northeast  of  Alamo  Heights,  lying  at  elevations  of 
from  750  to  800  feet. 

Heavy  gravel  deposits  overlie  the  highlands  in  the  north- 
eastern part  of  the  city  of  San  Antonio  and  are  well  exposed 
in  the  cut  made  by  the  Missouri,  Kansas  and  Texas  Railway 
as  well  as  in  pits  opened  up  for  road  material.  The  gravel 
beds  at  this  exposure  rest  upon  the  Midway  clays  and  are 
variable  in  thickness  from  a few  feet  to  a maximum  of  25  feet. 
The  upper  3 or  4 feet  are  in  places  caliche  cemented  and  form  a 
very  hard  rock.  At  lower  levels  the  gravel  is  less  firmly 
cemented  and  is  frequently  cross-bedded.  Lenses  of  clay  like- 


Geology  and  Mineral  Resources  of  Bexar  County 


69 


wise  are  observed,  one  of  which  is  a foot  thick  and  50  or  60  feet 
in  lateral  extent.  Many  of  the  flints  are  coated  with  a thin 
covering  of  calcium  carbonate ; on  some  of  the  flints,  especially 
the  smaller  ones,  this  coating  is  thicker  and  shows  concentric 
or  concretionary  layers.  Concretions  consisting  wholly  of 
calcium  carbonate,  or  with  merely  a nucleus  of  flint  or  other 
material,  are  present  in  this  exposure,  although  not  particularly 
abundant.  In  a pit  opened  for  road  material  on  the  Sulphur 
Springs  Road  near  this  cut,  the  deposit  consists  almost  wholly  of 
small  calcareous  concretions.  These  are  more  fully  described 
later  in  connection  with  the  description  of  similar  concretions 
from  other  localities. 

LEONA  (?)  FORMATION  AITD  PLAIN 

(Mid-Pleistocene  ?) 

The  term  L'eona  was  proposed  in  1900  by  Dr.  T.  W.  Vaughan, 
and  was  applied  to  a well  developed  flood  plain  in  the  Uvalde 
quadrangle  lying  at  a lower  level  than  the  Uvalde  plain*5  In 
Bexar  County  there  is  a well  developed  flood  plain  which 
very  possibly  is  contemporaneous  in  time  with  the  flood  plain 
to  which  the  name  Leona  has  been  applied,  and  which  is  there- 
fore tentatively  correlated  with  that  formation.  In  Uvalde 
County,  according  to  Vaughan,  the  position  of  the  Leona 
formation  is  intermediate  between  that  of  the  present  flood 
plain  and  the  Uvalde  plain.  In  Bexar  County  .the  conditions 
are  more  complicated,  in  that  there  are  three  Pleistocene  flood 
plains,  the  Leona  being  intermediate  between  the  older  and  the 
younger. 

The  relation  of  the  Leona  flood  plain  to  the  existing  streams 
is  perhaps  less  obvious  in  Bexar  than  in  Uvalde  County. 
However,  the  writer  offers  the  tentative  suggestion  that  this 
flood  plain  as  developed  on  the  broad  plains  on  which  Kelly 
Field  is  located,  is  associated  with  the  Leon  Creek  drainage. 
In  the  chapter  on  structure  it  is  shown  that  the  plunge  of  the 
structures  underlying  this  area  is  to  the  southwest.  Leon 
Creek  in  cutting  across  these  structures  has  therefore  tended 
to  shift  its  course  to  the  southwest.  The  effect  of  the  south- 

*U.  S.  Geol.  Surv.,  Uvalde  Folio,  p.  3,  1900. 


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University  of  Texas  Bulletin 


west  shifting  is  seen  at  the  present  time  in  the  high  bluffs  of 
this  creek  all  of  which  in  this  part  of  its  course  are  found  at  the 
right,  or  southwest,  side  of  the  stream.  The  tentative  explana- 
tion offered  is  that  the  Kelly  Field  plain  as  now  developed  was 
built  up  chiefly  by  Leon  Creek  or  its  predecessor  which  has 
gradually  shifted  and  is  still  shifting  its  course  in  a south- 
westward  direction.  The  plain  east  of  San  Antonio  may  in 
the  same  way  be  associated  with  the  Salado  Creek  drainage. 
The  high  bluffs  of  the  Salado,  like  those  of  the  Leon,  are  on  the 
right  bank,  the  plain  being  entirely  to  the  east  of  the  stream. 
That  the  San  Antonio  River  has  taken  so  small  a part  in  the 
development  of  this  plain  may  be  explained  by  the  fact  that 
its  drainage  system  scarcely  extends  back  to  the  Balcones 
escarpment  and  the  flood  waters  which  it  carries  are  less  ef- 
fective than  are  those  of  some  of  its  tributaries. 

The  materials  of  this  formation  are  extensively  used  for  road 
building.  Water  is  obtained  from  the  gravel  beds  of  the  forma- 
tion, chiefly  through  shallow  dug  wells. 

At  the  Castroville  Road  crossing  on  Leon  Creek  this  plain 
stands  at  a level  of  from  700  to  710  feet  above  sea,  or  from 
50  to  100  feet  below  the  level  of  the  plain  on  the  west  side  of 
Leon  Creek  already  described.  The  slope' of  the  plain  is  to 
the  south  or  southeast  and  amounts  to  between  ten  and  fifteen 
feet  per  mile.  Its  southern  margin  on  the  Somerset  and  Corpus 
Christi  roads,  six  or  seven  miles  south  of  San  Antonio,  ap- 
proximates six  hundred  feet  above  sea  level.  The  part  of  this 
plain  lying  to  the  east  of  Salado  Creek  has  a slope  from  north 
to  south  amounting  to  an  average  of  about  15  feet  per  mile. 

The  materials  of  this  plain  are  largely  gravel,  and  loam, 
although  over  a considerable  area  adjacent  to  the  San  Antonio 
River  and  Salado  Creek,  the  deposits  consist  largely  of  con- 
cretionary calcite  pebbles.  At  an  excavation  on  the  Quintana 
Road,  7 miles  southwest  of  San  Antonio,  there  is  exposed  of 
the  formation  15  or  18  feet.  The  materials  of  the  formation 
as  seen  in  this  exposure  are  stratified  and  consist  of  alternating 
layers  of  heavy  gravel  and  calcareous  sand.  The  deposits  are 
here  sufficiently  well  indurated  to  require  blasting  in  working. 

Tliickness:  Numerous  pits  for  road  material  have  been 

opened  into  gravel  deposits  of  this  plain.  In  these  pits  the 


Geology  and  Mineral  Resources  of  Bexar  County  71 

formation  as  a rule  has  a thickness  of  from  20  to  30  feet.  In 
some  of  the  wells  dug  into  these  gravels  they  have  been  found 
to  be  from  40  to  45  feet  thick.  Since  the  gravel  rests  upon  an 
eroded  surface  of  the  Upper  Cretaceous  and  Tertiary  forma- 
tions, they  may  be  expected  to  vary  greatly  in  thickness  from 
place  to  place. 

Physiographic  expression:  The  plain  formed  by  these 

deposits  has  a very  gradual  south  or  southeast  slope  amounting 
on  an  average  to  about  fifteen  feet  per  mile.  The  soils  include 
gravels  and  loams.  The  vegetation  on  the  uncleared  lands  is 
chiefly  mesquite.  The  elevation  of  this  plain  at  its  northern 
limit  is  about  750  feet  while  its  gradual  slope  carries  it  to  a 
level  of  about  650  or  600  feet  at  its  southern  limits. 

Common  fossils : No  fossils  have  been  found  by  the  writer  in 
this  formation,  although  the  presence  of  vertebrates,  particu- 
larly large  proboscidians,  has  been  reported  from,  excavations 
within  the  city  of  San  Antonio.  Inasmuch,  however,  as  the 
locality  in  question  is  near  the  headwaters  of  the  San  Antonio 
River  where  this  plain  merges  with  the  later  Pleistocene 
alluvial  plain,  an  exact  record  of  the  fossils  in  the  excavation 
is  necessary  in  order  to  make  sure  of  their  place  in  this, 
formation.  In  the  absence  of  fossils  the  plain  is  referred  doubt- 
fully to  about  the  middle  part  of  the  Pleistocene  period.  This, 
reference  is  based  on  the  fact  that  this  plain  lies  above  the 
late  Pleistocene  plain,  to  be  described,  and  on  the  fact  that 
the  materials  of  the  formation  are  not  infrequently  quite 
well  cemented.  Awaiting  a more  detailed  study  of  these 
deposits,  or  the  discovery  of  indigenous  fossils,  the  age  of 
the'  formation  can  scarcely  be  more  accurately  determined. 

Surface  exposures  and  local  details : The  largest  continuous 

development  of  this  plain  is  that  extending  from  Leon  Creek 
to  the  San  Antonio  River.  The  northern  margin  of  this  plain 
is  found  at  the  foot  of  the  hills  of  the  Austin  and  Taylor 
formations  near  or  south  of  the  Culebra  Road.  At  its  southern 
margin  the  plain  terminates  probably  by  surface  erosion  some 
six  or  seven  miles  south  of  San  Antonio,  although  near  the 
San  Antonio  River  remnants  of  the  plain,  too  limited  to  map, 
are  found  several  miles  forther  to  the  south.  Another  large 
development  of  this  plain  is  that  found  east  of  Salado  Creek 


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University  of  Texas  Bulletin 


and  extending  from  just  south  of  the  Austin  Road  crossing  to 
about  the  Goliad  Road  crossing. 

Good  exposures  of  the  gravels  of  this  plain  are  afforded  in  the 
pits  opened  for  road  materials.  In  these  pits  the  gravels  are  seen 
to  be  irregularly  stratified  or  cross-bedded,  often  with  alter- 
nated bands  of  coarser  and  finer  materials.  Most  of  the  gravel 
is  flint,  although  in  this  plain,  as  in  the  higher  Uvalde  plain, 
there  are  local  areas  in  which  the  materials  are  made  up  en- 
tirely of  small  calcium  carbonate  concretions.  On  this  plain 
such  concretions  are  seen  in  numerous  pits  on  the  west  side  of 
the  San  Antonio  River  and  on  the  east  side  of  the  Salado  River. 
In  the  valley  of  the  San  Antonio  River  this  plain  apparently 
merges  into  the  late  Pleistocene  and  recent  plains  within  the 
city  of  San  Antonio.  The  concretionary  gravels  are  subse- 
quently described. 

LATE  PLEISTOCENE  ALLUVIAL  DEPOSITS  . 

The  flood  plains  here  regarded  as  of  late  Pleistocene  age  are 
those  which  border  on,  and  have  an  obvious  relation  to,  the 
existing  streams  and  which  lie  above  the  present  flood  plain. 
The  most  pronounced  development  of  the  plains  of  this  kind  are 
those  of  the  Medina  River.  The  inorganic  materials  of  this 
plain  are  chiefly  silts  and  loams.  The  maximum  width  of  this 
late  Pleistocene  plain  is  found  on  the  Medina  west  of  the  central 
part  of  the  county  where  that  river  lies  near  the  boundary 
between  the  Cretaceous  and  Tertiary  deposits.  Farther  to  the 
east  where  the  river  is  cutting  through  the  Tertiary  formations, 
the  plain,  although  conspicuous,  is  not  as  a rule  so  wide.  The 
next  best  development  of  this  plain  is  that  which  borders 
Salado  Creek.  Here  also  the  maximum  width  of  the  plain  is 
found  where  the  creek  is  cutting  through  the  soft  upper 
Cretaceous  formations,  the  Taylor  and  Navarro.  In  the  Ter- 
tiary formations  the  plain  is  noticeably  narrowed.  On  the  San 
Antonio  River  there  is  but  a slight  development  of  this  plain. 

Thickness:  The  late  Pleistocene  flood  plain  deposits  attain  a 
maximum  thickness  on  the  Medina  River  of  about  50  feet.  On 
the  smaller  streams  they  are  of  lesser  development. 

Physiographic  expression : The  late  Pleistocene  plains  are 

seemingly  very  level,  although  as  a matter  of  fact  they  slope 


Univ.  of  Texas  Bull.  1932. 


PI.  I 


Pisolitic  gravel  in  the  Pleistocene  as  seen  in  pit  excavated 
for  road  material  near  the  Mission  Loop  Road  south  of  San 
Antonio  (See  page  75). 


LIBRARY 
OF  THE 

UNIVERSITY  OF  ILLINOIS 


Geology  and  Mineral  Resources  of  Bexar  County  73 

very  gradually  downstream,  the  rate  of  slope  amounting  to 
about  15  feet  per  mile.  The  soils  are  calcareous  loams,  and  the 
timber  growth  includes  considerable  hardwood  deciduous  trees. 

Common  fossils:  The  late  Pleistocene  and  the  Recent  deposits 
of  this  area  are  characterized  by  an  abundance  of  the  small  land 
snail,  Bulimulus  dealbatus  mooreanus*  which  is  common 
throughout  this  region  at  the  present  time.  The  presence  of 
this  snail  in  the  late  Pleistocene  deposits  and  its  absence  so  far 
as  observed  in  the  older  formations,  suggests  changed  climatic  or 
environmental  conditions  in  the  late  Pleistocene. 

In  addition  to  the  land  snails,  proboscidian  remains  have  been 
found  in  this  formation  at  a number  of  localities.  From  the 
lower  plain  on  the  east  side  of  Salado  Creek,  Baker  secured  the 
tooth  of  a mammoth,  Elephas  (Mss.  notes).  From  the  loam 
deposits  at  the  Frio  Road  crossing  on  Medina  River,  Mr.  C.  H. 
Vogt  collected  some  years  ago  a number  of  teeth  of  the  elephant 
together  with  -other  large  bones  probably  of  the  same  animal. 

Surface  exposures  and  local  details:  The  exposures  of  this 

late  Pleistocene  plain  are  found  bordering  all  the  larger  streams 
lying  from  25  to  35  feet  above  the  present  flood  plain.  The 
formation  is  readily  recognized  where  typically  developed  by 
the  presence  of  calcareous  loams,  containing  a great  abundance 
of  the  small  land  snail. 

In  mapping,  it  has  not  been  practicable  on  the  scale  used  to 
represent  this  formation  on  the  smaller  streams,  nor  to  show  its 
full  extent  upstream.  In  all  cases,  however,  it  narrows  in  width 
and  approaches  and  gradually  merges  into  the  present  flood 
plain.  Probably  the  maximum  thickness  of  the  formation  #is 
seen  on  the  Medina  River  near  the  Pleasanton  Road  crossing, 
where  typical  exposures  are  seen. 

CAVE  DEPOSITS 

Numerous  caves  exist  in  the  Cretaceous  and  Coman  chean 
limestones  of  this  county.  One  of  these  caves  on  the  property 
of  Mr.  A.  Friesenhahn,  about  20  miles  north  of  San  Antonio, 
has  been  found  to  contain  vertebrate  fossils.  The  presence  of 

*Kindly  identified  from  Bexar  County  specimens  by  Dr.  Paul 
Bartch. 


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University  of  Texas  Bulletin 


fossils  in  this  cave  was  discovered  some  years  ago  and  a small 
amount  of  collecting  from ‘the  cave  has  been  done  by  those 
locally  interested.  The  entrance  to  this  cave  at  the  present 
time  is  through  an  opening  extending  vertically  downward  for 
about  25  feet.  Formerly,  however,  there  was  another  and  dif- 
ferent opening  through  which  the  debris  that  partly  fills  the 
cave  has  been  washed  in.  In  addition  to  bones  of  small  animals, 
this  cave  contains  teeth  and  bones  of  the  elephant.  The  sabre- 
tooth tiger  has  also  been  reported.  With  these  bones  there  is 
associated  a number  of  specimens  of  the  land  snail,  Bulimulus 
dealbatus.  The  presence  of  this  fossil  suggests  that  the  cave 
deposits  probably  are  not  older  that  the  deposits  of  the  Medina 
flood  plain  which  this  snail,  so  far  as  present  observations  have 
shown,  first  appears  in  the  stratigraphic  succession.  The 
presence  of  the  snail  together  with  the  elephant  remains  sug- 
gests that  the  cave  deposits  are  probably  contemporaneous  with 
the  flood  plain  deposits  of  the  Medina  river.* 

RECENT 

The  Recent  deposits  of  this  area  are  chiefly  those  in  the  flood 
plains  of  the  streams.  Near  the  foothills  of  the  Edwards 
Plateau,  the  streams,  although  for  the  most  part  intermittent  in 
flow,  have  great  volume  and  velocity  for  a short  time  following' 
heavy  rains.  For  this  reason  the  beds  of  the  streams  near  the 
foothills  contain  a large  amount  of  flint  and  limestone  boulders 
and  rock  fragments,  derived  from  the  limestones  of  the  Balconies 
fault  zone  and  of  the  Edwards  Plateau.  In  passing  southward 
away  from  the  foothills,  the  materials  of  the  flood  plains  are 
found  to  contain  relatively  less  of  the  heavy  rocks  and  boulders 
and  relatively  more  of  the  silts  and  clay  loams  derived  from 
other  formations  through  which  the  stream  flows.  In  the 
southern  part  of  the  county  the  materials  of  the  flood  plain  of 
the  streams  are  chiefly  silt,  loam,  and  gravel. 

The  gravel  in  the  stream  beds  is  relatively  free  from  objection- 
able silt  and  for  this  reason  is  much  used  in  road  building 
especially  in  that  part  of  the  county  just  south  of  the  Balcones 
escarpment  where  the  largest  bodies  of  clean  gravel  are  found. 
Some  of  the  higher  flood  plains  are  utilized  in  farming,  since 

*Dr.  O.  P.  Hay  states  that  he  has  obtained  sixteen  species  of  fossils 
from  this  cave  (Letter  of  Nov.  6,  1919). 


Geology  and  Mineral  Resources  of  Bexar  County  75 

only  occasionally  are  they  overflowed.  On  the  Medina  River 
the  high  recent  flood  plain  has  frequently  been  utilized  in  pecan 
growing. 

In  mapping,  the  flood  plains  of  the  streams  have  been  in- 
cluded with  the  late  Pleistocene  flood-plain.  The  flood  plains  of 
all  of  the  streams  are  narrow  and  could  not  well  have  been  suc- 
cessfully represented  on  a map  of  the  scale  used  for  this  report. 

CALCAREOUS  CONCRETIONS  OF  THE  PLEISTOCENE 
OF  BEXAR  COUNTY  (PI.  1,  p.  72) 

In  connection  with  the  description  of  the  Pleistocene  flood 
plain  deposits  it  has  been  noted  that  calcareous  concretions  are 
present  and  in  places  are  very  abundant.  Concretions  of  this 
nature  are  particularly  numerous  in  the  deposits  referred  to  the 
Leona  formation  where  they  make  up,  over  considerable  area,  the 
greater  part  of  the  formation,  especially  in  areas  adjacent  to 
the  San  Antonio  River  and  Salado  Creek.  Similar  concretions 
are  found  locally  in  deposits  that,  judged  by  their  present  ele- 
vation above  the  stream  levels,  are  to  be  referred  to  the  Uvalde 
formation. 

In  the  literature  the  writer  has  been  able  to  find  only  two 
references  to  these  concretions,  both  of  which  unfortunately  are 
merely  abstracts  of  more  extended  papers.  The  earliest  of  these 
is  a brief  reference  in  an  informal  communication  on  various 
kinds  of  concretions  made  before  the  Geological  Society  of 
Washington  at  the  meeting  of  January  25,  1911,  by  C.  W. 
Hayes.  The  abstract  of  this  paper  given  in  Science  is  very 
brief,  that  part  of  it  referring  to  the  concretions  from  Bexar 
County  being  as  follows : 

Calcite  concretions  from  San  Antonio,  Texas.  These  occur  in 
great  abundance  in  the  “tepetate”  or  “caliche,”  a widespread  chalky 
limestone  formation,  produced  at  or  near  the  surface  in  semi-arid 
limestone  regions  by  the  ascent  of  wTater  through  capillary  action 
and  evaporation  with  deposition  of  the  dissolved  salts.  Ordinarily 
the  deposit  has  a platy  structure,  but  in  places,  as  at  San  Antonio, 
it  is  strongly  concretionary.* 

A paper  on  these  concretions  was  read  by  Alexander  Deussen 
at  the  California  meeting  of  the  Geological  Society  of  America, 


*Sci.  New  Ser.,  Vol.  XXXIII,  p.  550,  April  7,  1911. 


76 


University  of  Texas  Bulletin 


1915.  The  abstract  of  this  paper,  published  in  Volume  26,  No. 
4 of  the  Bulletins  of  the  Geological  Society  of  America  is  ^ery 
brief  and  does  not  include  the  author’s  conclusions. 

However,  in  reply  to  an  inquiry  by  the  writer,  Deussen  has 
stated  that  his  investigations  led  him  to  the  conclusion  that  these 
concretions  were  formed  from  thermal  springs.* 

The  suggestion  that  these  concretions  were  formed  from 
thermal  springs  appeals  to  the  writer  as  both  reasonable  and 
probable.  It  is  probably  not  accidental  that  these  concretions 
lie  down  stream  from  the  location  of  the  pronounced  breaks  or 
faults  from  which  springs  now  issue  supplying  the  present 
streams  of  San  Antonio  and  Salado.  It  is  true  that  these  faults 
cross  other  creeks,  as  for  instance  Leon  Creek,  but  in  the  case 
of  Leon  Creek  the  faults  are  so  nearly  sealed  as  to  allow  very 
little  water  to  emerge  at  the  surface,  and  on  Leon  Creek  there 
is  found  no  accumulation  of  these  concretions  such  as  are  found 
near  San  Antonio  and  Salado  Creeks.  That  the  water  of  these 
.springs  during  the  Pleistocene  period  was  thermal  or  at  least 
somewhat  warmer  than  at  present  is  probable.  If  the  deep 
waters  emerging  at  that  time  were  thermal,  the  continued  cir- 
culation of  water  through  the  rocks,  emerging  at  the  springs 
during  and  since  the  Pleistocene  would  tend  to  reduce  both  the 
temperature  and  the  amount  of  solids  carried  in  solution  by 
the  water.  It  may  be  noted  in  'this  connection  that  the  waters 
of  the  Comanchean  formations  at  the  present  time  are  found  to 
be  warm  and  to  carry  a heavy  load  of  solids  in  solution  in  wells 
drilled  a few  miles  southeast,  that  is  down  the  dip,  from  the 
existing  springs. 

The  area  occupied  by  these  concretions  includes  a narrow  belt 
on  either  side  of  the  ‘San  Antonio  River  for  several  miles  south 
of  San  Antonio,  and  a much  larger  belt  lying  at  the  northeast 
side  of  the  Salado  Creek.  This  belt  on  Salado  Creek  has  a width 
of  two  or  three  miles  and  extends  for  five  or  six  miles  south  of 
the  Seguin  Road  crossing. 


*Letter  of  August  18,  1919. 


Geology  and  Mineral  Resources  of  Bexar  County  77 
STRUCTURAL  GEOLOGY 

The  formations  in  Bexar  County,  both  those  of  the  Cretaceous 
and  Tertiary,  dip  toward  the  Gulf  Coast.  The  rate  of  dip, 
however,  is  changed  and  the  county  is  divided  both  structurally 
and  physiographically  into  two  very  distinct  provinces  along 
the  line  already  referred  to,  known  as  the  Balcones  Escarp- 
ment, which  in  this  county  faces  south-southeast.  The  struc- 
tural conditions  are  very  different  in  these  two  provinces. 
North  of  the  Balcones  Escarpment,  the  formations  depart  but 
little  from  the  horizontal  position,  the  rate  of  dip  south  of  the 
Colorado  River  having  been  estimated  by  Hill  and  Vaughan  to 
be  not  more  than  10  feet  per  mile.*  The  structure  in  the  coastal 
plains  area  of  this  county  is  much  more  complicated  than  is 
that  north  of  the  Balcones  Escarpment,  being  affected  both  by 
faulting  and  by  folding.  At  the  inner  or  north  margin  of  the 
Coastal  Plains  area  are  large  faults,  while  farther  to  the  south 
are  other  faults  varying  from  small  to  .large,  accompanied  by 
folds.  The  downthrow  in  most,  although  not  in  all,  of  the 
faults,  and  in  the  largest  faults,  is  to  the  southeast  or  coastal 
side.  The  structures  are  in  some,  perhaps  all,  instances  asym- 
metrical, the  longer  slope  being  on  the  southeast  side.  The  com- 
bined effect  of  faulting  and  dipping,  although  varying  from 
place  to  place,  results  on  the  whole  in  carrying  the  formations 
rapidly  to  a lower  level  in  passing  toward  the  coast. 

The  lines  of  faulting  and  folding  in  the  coastal  plains  area 
either  approximately  parallel  the  main  or  first  large  fault  of 
the  Balcones  fault  zone,  or  they  diverge  to  the  south,  and  plunge 
to  the  southwest.  The  southwest  plunge  of  the  formations,  as 
well  as  the  divergence  to  the  south  from  the  line  of  the  main 
fault,  are  possibly  incident  to  the  change  of  direction  of  the 
fault  zone  in  this  and  the  adjoining  county,  to  which  reference 
has  already  been  made. 

LOCATION  OF  PRINCIPAL  FAULTS 

The  first  large  fault  of  the  fault  zone  is  that  which  brings  the 
Edwards  formation  against  the  Glenrose.  Helotes  Creek 
at  the  Bandera  Road  crossing  flows  in  this  fault ; the  downthrow 
side  of  the  fault,  the  Edwards  limestone,  being  exposed  in  the 

*U.  S.  Geol.  Surv.,  18th  Ann.  Rpt.  Part  2,  p.  258,  1898. 


78 


University  of  Texas  Bulletin 


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left  bank  of  the  stream.  The  following  data  afford  an  approxi- 
mate estimate  as  to  the  amount  of  throw  of  this  fault: 

The  surface  elevation  at  the  deep  well  on  the  Leon  Springs 
Reservation  is  about  1156  feet  above  sea  level.  In  this  well 
the  pre-Cretaceous  schists  were  entered  at  the  depth  of  1015  feet 
or  at  the  actual  level  of  about  140  feet  above  sea.  The  elevation 
of  the  second  deep  well  located  on  the  Camp  Bullis  Reservation 
about  six  miles  farther  south,  is  less  definitely  known,  but  is 
probably  about  1050  feet  above  sea.  In  this  well,  which  is  one 
or  two  miles  east  of  the  first  or  main  fault  of  the  Balcones  fault 
zone,  the  pre-Cretaceous  schists  were  entered  -at  the  depth  of 
1799  feet,  or  at  the  actual  level  of  about  750  feet  below  sea.  The 
difference  in  elevation  of  the  top  surface  of  the  schist  at  these 
two  localities,  amounting  to  about  890  feet,  is  doubtless  due  in 
part  to  irregularities  of  the  top  surface  of  the  schists,  but  a part 
and  probably  the  greater  part  of  this  difference  in  elevation  is  ac- 
counted for  by  faulting,  since  the  wells,  as  already  stated,  are 
separated  by  the  large  fault  of  the  Balcones  fault  zone. 

A second  and  probably  more  nearly  exact  measurement  of  the 
throw  of  this  first  large  fault  is  obtained  by  comparing  the 
records  of  these  two  wells.  At  the  Leon  Springs  well  the  Glen- 
rose  formation  rises  in  the  hills  to  an  elevation  of  1350  feet  or 
more  above  sea.  In  the  well  on  the  Camp  Bullis  reservation  this 
formation  is  first  recognized  by  characteristic  fossils  at  the 
depth  of  584  feet  below  the  surface,  or  at  the  elevation  of  about 
466  feet  above  sea  level.  There  is  therefore  an  interval  of  be- 
tween 600  and  800  feet  representing  the  downthrow  of  this  fault, 
together  with  dips  incidental  to  the  faulting. 

South  of  the  first  large  fault  are  numerous  others,  small  and 
large.  The  amount  of  throw  of  these  faults  varies  from  a few 
feet  to  between  400  and  500  feet;  the  downthrow  of  some  of 
the  faults  is  to  the  north  side  but  the  usual  downthrow  and  the 
maximum  downthrow  is  to  the  south  side.  A study  of  the  well 
records  indicates  that  in  addition  to  numerous  small  faults  there 
are  several  heavy  faults  or  narrow  zones  of  multiple  faulting. 
One  of  these  faults  or  fault  zones  passes  north  of  and  approxi- 
mately parallels  the  Castroville  Road  west  of  San  Antonio  and 
in  some  way  seems  to  involve  the  formation  of  the  basin  of  El- 
mendorf  Lake  and  possibly  also  of  West  End  Lake.  Well 
records  in  the  vicinity  of  Elmendorf  Lake  in  particular  are  very 


Geology  and  Mineral  Resources  of  Bexar  County  81 

unusual  and  discordant,  giving  results  that  can  be  accounted  for 
only  by  complicated  faulting,  breaking,  and  displacement  of 
the  formations.  Across  this  zone  of  faulting  there  is  a change 
of  level  in  the  formations,  as  indicated  by  well  records,  amount- 
ing to  about  400  feet  within  a mile  or  less.  In  the  western  part 
of  the  county  this  fault  zone  may  be  located  both  by  topography 
and  surface  exposures.  The  line  of  hills  seen  north  of  the  Cas- 
troville  Road  in  the  western  part  of  the  county  is  formed  from 
the  Austin  formation.  The  more  or  less  dissected  plain  crossed 
by  the  Castroville  Road  lies  chiefly  on  the  Navarro  formation. 
Exposures  near  the  fault  line  are  seen  on  the  Masterson  ranch 
north  of  the  Castroville  Road  on  Lucas  Creek. 

A large  fault  with  the  usual  northeast- southwest  trend  passes 
through  the  northwestern  part  of  San  Antonio.  This  fault  is 
readily  located  by  topography,  surface  exposures,  and  well  rec- 
ords. From  San  Antonio  to  the  east  county  line  the  upthrow 
of  this  fault  brings  the  Austin  formation  to  the  surface  while  on 
the  downthrow  side  is  the  Taylor  formation.  The  surface 
topography  revealing  the  upthrow  side  is  the  range  of  Austin 
Hills  extending  northeast  from  San  Antonio.  The  exposures 
which  reveal  the  fault  have  already  been  mentioned  and  include 
the  exposures  of  the  Austin  formation  seen  in  Brackenridge 
Park  at  the  north  city  limits,  and  on  Salado  Creek  and  trib- 
utaries at  the  Austin  Road  crossing  already  described.  The 
exposures  of  the  Taylor  formation  on  the  downthrow  side  of  the 
fault  are  seen  on  River  Avenue.  An  approximate  measurement 
of  the  amount  of  throw  of  this  fault  is  obtained  from  two  wells 
in  the  northeastern  part  of  San  Antonio.  In  a well  located  in 
Brackenridge  Park  at  the  north  city  limits,  the  Comanchean 
was  reached  at  the  actual  level  of  554  feet  above  sea.  In  the 
well  drilled  for  Fort  Sam  Houston  water  supply,  on  Hackberry 
Street,  about  one  mile  farther  south,  these  formations  were 
entered  at  the  actual  level  of  124  feet  above  sea.  There  is  thus  a 
drop  in  elevation  of  430  feet  within  a mile.  Whether  this  change 
in  level  is  due  to  a single  large  fault,  or  to  a succession  of 
smaller  faults,  or  to  combined  faulting  and  dipping,  has  not 
been  determined. 

Near  the  southern  limits  of  San  Antonio  is  another  zone  of 


6-Bex. 


82 


University  of  Texas  Bulletin 


faults  or  rapid  dips  where,  as  indicated  by  well  records,  the 
formations  pass  in  going  southeast  to  a level  about  350  feet 
lower  in  a distance  of  three-fourths  of  a mile  or  less.  North  of 
the  fault  zone  the  Comanchean  is  entered  at  from  900  to  950 
feet  from  the  surface,  while  south  of  the  fault  zone  these 
formations  are  entered  at  from  1200  to  1250  feet  from  the 
surface.  This  zone  of  faulting  is  located  chiefly  by  wells  the 
location  of  which  is  indicated  by  map  entries  — 322  and  — 338 
(north  of  the  fault),  and  — 680  and  — 679  (south  of  the 
fault). 

These  several  fault  lines  do  not  seem  to  be  continuous  as 
equally  strong  faults  entirely  across  the  county.  On  the  con- 
trary, some  of  them  appear  to  pass  from  strong  dips  into 
faults  and  again  into  dips  or  a succession  of  small  faults,  a 
few  of  which  have  been  located  either  by  exposures  or  by  well 
Records,  but  many  of  which  are  obscured  at  the  surface.  At 
least  two  small  faults  cross  the  Fredericksburg  Road  within 
two  or  three  miles  south  of  the  main  Balcones  fault.  One  of 
these  may  be  seen  in  a cut  in  the  San  Antonio  and  Aransas  Pass 
Railway  about  14  miles  north  of  San  Antonio.  The  trend  of 
this  fault  at  this  exposure  is  north  30°  east.  The  upthrow  m 
this  instance  is  at  the  south  side,  the  Buda  formation  at  the 
south  side  of  the  fault  being  thrown  against  the  Eagleford 
formation  at  the  north  or  downthrow  side.  Faults  near  the 
Austin  Road  crossing  on  Salado  Creek  have  already  been 
described.  In  the  cut  made  by  the  Southern  Pacific  branch 
line  to  Camp  Travis,  near  the  east  limits  of  San  Antonio,  is 
a fault  which  trends  about  north  50°  east.  The  downthrow  of 
this  fault  is  probably  to  the  south.  Two  wells  drilled  at 
Conception  Mission  indicate  the  location  of  a small  fault  having 
a downthrow  to  the  south  of  about  50  feet.  A small  fault  or 
very  abrupt  dip  is  seen  at  an  exposure  on  the  Pleasanton 
Road,  eight  miles  south  of  San  Antonio  and  near  the  southern 
margin  of  the  Alta  Vista  oil  field.  The  trend  is  here  north 
60°  east. 

STRUCTURALLY  HIGH  AREAS 

Associated  with  and  more  or  less  definitely  limited  by  the 
faults  are  well  marked  structurally  high  areas,  lifted  blocks,  or 


Geology  and  Mineral  Resources  of  Bexar  County  83 

folds,  the  location  of  which  is  recognized  both  on  surface  ex- 
posures and  on  well  records.  Three  such  pronounced  structures  • 
have  been  recognized  in  the  north  part  of  the  county,  which  for 
convenience  of  reference  may  be  known  as  the  Culebra,  San 
Antonio  and  Alta  Vista  structures.  Aside  from  or  within  these 
larger  structures  are  smaller  structures,  the  location  of  which 
requires  more  detailed  mapping  than  is  attempted  in  this 
report.  In  the  southern  part  of  the  county  it  becomes  difficult 
to  interpret  structural  conditions,  owing  to  the  few  well  records 
and  limited  surface  exposures  available.  It  seems  probable, 
however,  that  another  structure  similar  to  those  described  is 
found  south  of  the  Medina  River,  its  position  being  indicated  by 
the  J.  K.  Lamb  well,  elsewhere  described. 

THE  CULEBRA  STRUCTURE 

The  first  of  the  pronounced  high  areas  -is  a relatively  broad 
structure,  the  axis  of  which  lies  some  six  miles  south  of  the 
Balcones  Escarpment.  This  high  area  is  recognized  both  on 
surface  exposures  and  on  well  records.  On  the  crest  of  this 
structure  in  the  western  part  of  the  county  the  Austin  forma- 
tion lies  at  the  surface,  while  both  to  the  north  and  south  the 
Taylor  formation  lies  at  the  surface.  The  structure  is  equally 
well  indicated  by  well  records.  The  actual  level  of  the  Del  Rio 
formation  on  the  north  side  of  this  structure  near  the  west 
county  line  is  about  150  feet  above  sea  (well  of  J.  Benke).  The 
same  formation  three  miles  southeast  of  this  place  lies  about 
300  feet  higher  (well  of  H.  Uhl).  The  axis  of  the  structure  ap- 
pears to  lie  another  one  or  two  miles  farther  south  and  hence 
somewhat  higher  than  in  the  Uhl  well.  At  the  east  side  of  the 
structure  the  Del  Rio  has  again  dropped  to  about  170  feet  above 
sea  level  (well  at  fuller’s  earth  plant).  Several  well  records  are 
available  on  and  near  the  Culebra  Road,  which  crosses  this 
structure  obliquely  in  passing  from  the  west  county  line  to  San 
Antonio.  The  axis  of  the  structure  is  crossed  on  this  road  about 
14  miles  northwest  of  San  Antonio.  Here  the  Del  Rio  forma- 
tion lies  at  the  actual  level  730  feet  above  sea  (well  of  Mrs. 
A.  Voight).  Passing  southeast,  this  formation  drops  down  to 
170  feet  above  sea  level  in  a distance  of  six  miles  (well  of  A. 
Skolout).  Beyond  this  well  to  the  southeast  is  the  fault  with 


84 


University  of  Texas  Bulletin 


a downthrow  of  as  much  as  400  feet  to  which  reference  was 
, made  earlier  in  this  paper. 

It  is  difficult  to  determine  whether  this  structurally  high  area 
represents  an  anticline  in  the  usual  sense  of  the  term,  or  a 
fault  block.  If  the  latter,  the  block  is  limited  at  either  side 
not  by  a single  large  fault,  but  by  a succession  of  small  or  step 
faults.  That  there  are  faults  at  the  north  side  of  the  area  with 
the  downthrow  to  the  northwest  is  shown  by  the  fault  already 
referred  to  seen  in  the  railway  cut  near  the  north  side  of  the 
structure.  It  is  probable  that  this  structurally  high  area  is 
produced  by  a combination  of  faulting  and  folding. 

The  wells  from  which  data  have  been  obtained  and  used  in 
mapping  this  structure  include  those  indicated  by  map  entries 
150,  360,  369,  455,  496,  555,  730,  715,  685,  560,  545,  580,  492, 
270,  188,  170,  85,  16. 

/ 


THE  SAN  ANTONIO  STRUCTURE 


A second  notably  high  area  having  a northeast- 
southwest  trend  passes  through  the  northwestern  corner  of 
the  city  of  San  Antonio.  From  San  Antonio  northeast  the 
surface  exposures  on  this  structure  are  those  of  the 
Austin  formation,  forming  the  range  of  Austin  Hills  already 
described.  Near  the  western  limits  of  San  Antonio,  owing  to 
the  southwest  plunge  the  Taylor  comes  to  lie  on  the  structure 
while  exposures  probably  of  the  Navarro  are  seen  at  the  north 
side  on  the  Culebra  Road,  5.4  miles  from  San  Antonio.  From 
near,  the  west  limits  of  San  Antonio  to  Leon  Creek  the  structure 
is  concealed  by  the  flood-plain  deposits,  and  when  again  seen 
at  and  beyond  Leon  Creek,  the  Taylor  formation  has  been  car- 
ried by  the  southwest  plunge  below  the  surface,  the  exposures 
being  largely  if  not  entirely  those  of  the  Navarro  formation. 
The  gas  field  west  of  Leon  Creek  appears  to  be  located  within 
this  structure.  Beyond  Medina  Creek  the  structure  has  not 
been  located  either  by  surface  exposures  or  by  well  records,  and 
it  is  not  known  whether  it  flattens  out  or  its  position  is  merely 
in  doubt  from  lack  of  suitable  data. 

The  best  exposures  of  this  structure  are  those  seen  in  the 
right  bank  of  Leon  Creek  which  crosses  the  structure  south  of 


Geology  and  Mineral  Resources  of  Bexar  County  85 

Kelly  Field  from  the  Castroville  to  the  Quintana  Road  crossings. 
At  the  Castroville  Road  and  for  at  least  two  miles  farther  down 
Leon  Creek,  the  dips  are  to  the  northwest.  From  near  or  west 
of  the  Pearsall  Road  to  the  Quintana  Road,  the  dips,  often 
strong,  are  to  the  southeast.  A green  glauconitic  sandstone 
ledge  which  serves  as  a horizon  marker  in  these  sections  is  seen 
both  at  the  west  and  the  east  sides,  but  is  wanting  on  account  of 
erosion  from  the  central  part  of  the  structure  at  the  Leon 
Creek  crossing.  The  exposures  east  of  San  Antonio  which  best 
locate  this  high  area  are  seen  on  the  Perin-Beitel  Road  from 
Fratt  to  Wetmore.  At  Fratt,  exposures  are  seen  on  this  road 
which  probably  represent  the  upper  marly  phase  of  the  Austin 
formation.  On  the  hills  one  and  a half  miles  north  of  Fratt  are 
seen  exposures  representing  the  hard  limestones  of  the  lower 
half  of  the  Austin  formation,  while  in  the  valley  next  northwest 
of  these  hills  are  exposures  of  either  the  upper  part  cf  the 
Austin  or  the  Taylor  formation.  Near  Elmendorf  Lake  at  the 
west  limits  of  San  Antonio,  this  stricture  is  interrupted  by  a 
break  or  fault  in  which  the  formations  are  displaced  as  much  as 
about  400  feet. 

The  wells  by  which  this  structure  is  located  include  those  in 
dica:ed  by  map  entries  250,  485,  568,  317,  306,  and  69. 

THE  ALTA  VISTA  STRUCTURE 

Three  of  the  oil  fields  of  Bexar  County,  namely  the  Alta  Vista, 
Mission,  and  Somerset  fields,  are  so  placed  with  respect  to  pre- 
vailing structural  lines  in  this  county  as  to  suggest  that  they 
are  possibly  located  on  the  same  structure.  If  this  is  true,  in 
this  structure  as  in  the  two  already  described,  there  is  a dis- 
tinct southwest  plunge.  The  heavy  oils  of  the  Alta  . Vista  and 
Mission  fields  are  obtained  from  the  Austin  formation  at  the 
actual  level  of  from  450  to  550  feet  below  sea  level.  In  the 
Sommerset  field  the  lighter  oils  are  obtained  from  either  the 
Taylor  __or  the  Navarro  formations  at  the  actual  level  of  from 
400  to  700  feet  below  sea.  To  the  northeast  of  Salado  Creek, 
this  structure,  if  we  may  rely  on  the  rather  limited  well  records 
available,  turns  more  to  the  north,  resembling  in  this  respect 
the  Culebra  structure.  It  seems  also  to  be  interrupted  near  the 


86 


University  of  Texas  Bulletin 


Seguin  Road  crossing  by  a fault.  On  this,  however,  the  well 
records  available  are  limited,  and  the  mapping  of  this  break  is 
provisional.  It  is  similar,  however,  to  the  interruption  of  the 
San  Antonio  structure  already  described.  See  wells  No.  57,  p. 
138;  94,  p.  140;  120,  p.  165;  124,  p.  167;  and  160,  p.  197. 

THE  GEOLOGIC  MAP 

On  the  geologic  map  are  represented  the  surface  exposures  of 
the  formations  of  this  county  in  such  detail  as  is  practicable  on 
a map  of  this  scale.  One  of  the  problems  to  be  met  in  mapping 
this  area  is  the  disposition  to  be  made  of  the  flood-plain  de- 
posits which  more  or  less  completely  mantle  the  whole  of  the 
coastal  plains  division  of  the  county.  Since  the  chief  object  of 
this  report  is  to  describe  the  general  geology,  these  flood-plain 
deposits  have  been  disregarded  in  mapping,  except  where  suf- 
ficiently well  developed  to  completely  obscure  the  underlying 
formations  over  considerable  areas.  The  low  and  relatively 
recent  flood-plains  have  been  shown  where  best  developed  bor- 
dering the  larger  water  courses;  of  the  next  older  and  higher 
deposits,  the  Leona  formation,  there  have  been  shown  on  the 
map  the  large  areas  lying  southwest,  south,  and  southeast  of 
San  Antonio ; of  the  highest  plain,  referred  to  the  Uvalde  forma- 
tion, there  have  been  shown  some  areas  in  which  the  formation 
occupies  uninterruptedly  several  square  miles.  All  of  these 
flood  plains  are  more  extensive  than  is  here  shown. 

Because  of  the  presence  of  these  surface  materials,  the 
boundary  between  the  successive  marine  formations  is  neces- 
sarily placed  in  parts  of  the  county  on  data  from  limited  ex- 
posures, supplemented  by  well  records.  Where  the  surface  is 
entirely  obscured,  the  approximate  boundary  of  the  underlying 
marine  formations  has  in  some  instances  been  indicated  by 
broken  lines,  the  data  for  placing  the  boundary  being  obtained 
chiefly  from  well  records.  As  information  is-  accumulated  on 
the  geology  of  this  and  the  adjoining  counties,  the  boundary 
lines  of  the  formations  can  be  more  exactly  determined. 

In  mapping  structure  the  Del  Rio  has  been  used  as  a key 
horizon  and  the  contours  are  drawn  as  on  the  top  surface  of 
this  formation.  In  using  well  records  and  reducing  elevations 


Geology  and  Mineral  Resources  of  Bexar  County  87 

to  sea  level  it  has  been  necessary  to  determine  the  approximate 
surface  level  of  the  wells  from  the  topographic  map.  In  that 
part  of  the  county  for  which  there  is  no  topographic  map  the 
elevations  for  wells  near  the  public  roads  have  been  obtained 
from  the  profiles  of  public  roads  made  by  the  County  Engineer 
of  Bexar  County,  kindly  made  accessible  for  this  purpose.  In 
a few  wells  not  on  the  area  topographically  mapped  and  remote 
from  the  public  roads,  an  estimate  of  the  elevation  has  been 
secured  by  data  showing  the  level  to  which  the  artesian  water  of 
the  Georgetown-Edwards  formations  will  rise  in  wells.  The 
static  head  of  this  water  brings  it  to  an  actual  level  usually 
between  665  and  685  feet  above  sea,  affording  an  approximate 
basis  for  estimating  the  surface  elevation  at  the  well.  These 
methods  of  determining  levels  have  introduced  a possible  small 
error.  A much  larger  possible  error  is  found  in  the  well  records 
themselves.  As  t is  well  known,  many  well  records  afford  only 
approximate  data  as  to  the  depth  at  which  formations  are 
entered.  While  the  wells  of  Bexar  County  afford  unusually 
reliable  data,  yet  it  has  been  found  in  a number  of  instances 
that  two  logs  of  the  same  well,  derived  from  different  sources, 
differ  to  some  extent.  However,  the  limit  of  error  both  from 
approximate  levels  and  from  well  logs,  when  carefully  checked,, 
is  not  large  as  compared  to  the  contour  interval  of  100  feet  used' 
in  making  the  sub-structure  map. 

INDEX  TO  LEVELS  ON  THE  DEL  RIO  FORMATION 

The  numbers  entered  on  the  geologic  map  give  the  level  of 
the  top  of  the  Del  Rio  formation  ^above  or  below  sea,  the  levels 
below  sea  being  indicated  by  a minus  sign  preceding  the  num- 
ber. In  the  following  list  the  map  entry  numbers  are  ar- 
ranged serially  and  for  each  entry  there  is  given  the  name  of 
the  owner  of  the  well  and  also  the  number  which  will  serve  as 
an  index  reference  to  the  more  complete  data  given  in  the 
chapter  on  well  records.  The  question  mark  following  certain 
of  the  numbers  on  the  map  indicates  that  the  record  is  in  doubt, 
the  level  of  the  Del  Rio  having  been  in  some  instances  estimated 
from  the  level  at  which  some  of  the  overlying  formations  were 
reached. 


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University  of  Texas  Bulletin 


Map  Entry  Owner  Well 

Number  Number* 

5 Southern  Ice  Co Ill 

6 Bexar  County  Courthouse 17 

16  F.  Masterson  well  80 

25  Geunther  Milling  Co 41 

• 30  Roy  Hearne  51 

60  Lone  Star  Brewing  Co 7 6 

69  Government  well,  Hackberry  St 45 

7 4 Artesian  Ice  Co 8 

82  Southwestern  Land  Corporation 114 

-82  T.  F.  Brady  22 

85  Medina  Fullers  Earth  Co 82 

88  Salado  Water  Supply  Co 98 

88  Soutliwester  Land  Corporation  113 

90  Geo.  Brackenridge  23 

-100  G.  F.  Trice  133 

-110  H.  Van  Dale  136 

115  H.  Heine  54 

—115  San  Antonio  Steam  Laundry 105 

—120^  Shattuck  well  109 

150  Mrs.  Kate  Benke  14 

120  Roy  Hearne  52 

170  A.  Skolaut  110 

188  Ed  Peffman  88 

-190  J.  H.  Quinn  90 

200  Mrs.  Mackintosh  7 6 

210  Paul  Hartman  . . , 50 

213  St.  Louis  College  97 

215  Southern  Pacific  Ry.  Schertz  (Guadalupe  Co) 

-215  Oscar  Kreutch  71 

226  Roy  Hearne  . 33 

227  H.  Brendle  24 

237  Chas.  Matyear  81 

239  J.  D.  Stephenson  116 

—245  Community  well,  Cuppers  Lane 31 

250  Ross  Davis  32 

254  M.  K.  T.  Ry.,  Landa 86 

257  A.  Koeps  70 

260  Ed.  E.  Basse  55 

260  L.  M.  Hubble  64 

270  Chas.  Hease  75 

-270  S.  A.  and  A.  P.  Ry 100 

-280  Collins  Gardens  . 30 

-285  H.  J.  Ackerman  3 

306  H.  Benz  15 


*The  wells  to  which  these  numbers  refer  are  described  on  pages 
129  to  197. 


Gfeology  and  Mineral  Resources  of  Bexar  County  89 

Map  Entry  Owner  Well 

Number  Number 

-310  Acme  Irrigation  Co 4 

-315  R.  H.  Hofheintz 59 

317  Government  well.  Aviation  post  44 

-320  D.  G.  Allen  6 

—322  Artesian  Water  Co 11 

-323  J.  H.  Terrell  125 

-328  D.  J.  Allen 7 

—338  Steves  Garden  118 

-339  Gates  and  Co 40 

350  Southern  Pacific  Ry 112 

-350  Glen  Carney  26 

353  Dickenson  well  33 

-355  Dr.  Sullivan  122 

360  N.  Kallison  63 

367  H.  H.  Statte  115 

369  Mrs.  C.  Hoffman  58 

-36  9 Lady  of  the  Lake  Academy 72 

-405  L.  S.  Toft  130 

-410  C.  C.  Clamp  27 

-415  West  Gardendale 140 

-418  H.  Herff  56 

435  H.  Schumeier  108 

440  J.  Locke  75 

449  H.  Prinz  89 

-453  J.  T.  Blank  15 

455  H.  Uhl  . . .134 

460  Waring  Estate  139 

470  Chris  Weir  142 

470  Hohnenberger  well  62 

—472  W.  F.  Leigler  74 

485  Alex  Lorenz  77 

4 92  H.  Steubing  117 

496  A.  E.  Goforth  43 

497  San  Antonio  City  well  113 

498  Joe  Friesenhahn  39 

520  O.  J.  Worsbach  144 

54  5 A.  Boerman  20 

555  J.  Widener  141 

560  D.  Boerman  21 

568  F.  Grote  46 

580  E.  J.  Altgelt 11 

620  H.  Bruhn  25 

655  Jud  Harrison  49 

-679  San  Antonio  City  Water  Supply 101 

680  August  Rumper  . . 95 

-680  R.  Tommins  131 

685  Pete  Tezel  128 


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University  of  Texas  Bulletin 


Map  Entry  Owner  Well 

Number  Number 

715  Louis  Tezel  127 

730  A.  Voight  138 

735  E.  J.  Altgelt  . . . . 10 

-750  Terrell  Hot  Wells  124 

-800  Wolfe  & Elder 160 

—816  A.  J.  Ridder  93 

-841  Kearney  Oil  & Pipe  Line  Go 67 

-870  Hot  Wells  Hotel  63 

-880  Wm.  Voght  137 

—888  Superior  Oil  Co 123 

—888  Anton  Ripps  94 

—915  Holz  well  60 

—920  Medina  Oil  Co 83 

950  H.  T.  Biering  16 

—1000  Perrinot  well  156 

-1005  Winters  and  Kreugel  143 

1050  Government  well,  Camp  Bullis  2 

—1070  Hill  and  Roby  51 

—1130  Steves  well  120 

—1380  Townsite  well  132 

-1500  J.  K.  Lamb  149 

-1685  Blue  Wing  Club  well  19 

—1827  Mathey  well  151 


NOTES  ON  EXPOSURES  SEEN  ON  THE  PUBLIC  ROADS 

It  has  seemed  worth  while  to  place  on  record  here  certain 
data  accumulated  in  connection  with  the  field  work  and  used 
in  the  preparation  of  the  geologic  and  other  maps.  These 
notes  were  for  the  most  part  taken  while  traveling  the  several 
main  roads  of  the  county,  and  for  convenience  of  reference 
are  reported  in  the  order  of  roads  out  from  San  Antonio  to 
the  north,  east,  south,  and  west.  Mileage  in  all  instances 
refers  to  distance  from  the  Court  House  in  San  Antonio. 
Presented  in  this  form  the  notes  will  perhaps  be  of  service  to 
the  people  of  the  county  who  travel  these  roads,  as  well  as  to 
the  large  number  of  visitors  who  come  each  year  to  this  part  of 
the  State. 

Blanco  Road:  The  Blanco  Road  runs  approximately  due  north 

from  San  Antonio  to  the  county  line.  From  the  Bexar  County 
court-house  this  road  lies  within  the  valley  of  the  San  Antonio 
River  for  a distance  of  about  1.4  miles.  Underlying  the  stream 
deposits  of  this  valley  at  this  crossing  is  chiefly  the  Taylor  forma- 
tion. In  the  western  part  of  San  Antonio,  from  1.4  to  2.5  miles 


Geology  and  Mineral  Resources  of  Bexar  County  91 

from  the  courthouse,  the  road  passes  over  the  San  Antonio  struc- 
ture previously  described;  the  formation,  beneath  the  surface  grav- 
els, being  the  Austin  chalk.  From  2.5  to  3.7  miles  is  a gravel- 
covered  and  partially  gravel-filled  valley,  the  underlying  formation 
being  probably  the  Taylor  as  indicated  by  exposures  on  other  roads. 
Between  3.7  to  4.7  miles  from  San  Antonio  this  road  passes  onto 
the  large  zone  of  exposures  of  the  Austin  formation  and  continues 
chiefly  or  entirely  on  this  formation  to  the  valley  of  Salado  Creek, 
about  10  miles  from  San  Antonio.  . In  the  bluffs  of  Salado  Creek, 
the  Austin,  Eagleford,  and  Blida  formations  are  exposed  as  al- 
ready described.  These  formations  are  again  seen  on  the  hill  north 
of  Salado  Creek.  Exposures  of  the  Del  Rio  were  not  observed  on 
this  road  but  the  formation  is  crossed  over  probably  between  11 
and  12  miles  out  from  San  Antonio,  its  zone  of  outcropping  being 
represented  by  a valley  beyond  which  are  seen  the  Georgetown- 
Edwards  limestones.  The  Glenrose  formation  comes  in  on  this 
road  about  19  miles  from  San  Antonio. 

For  the  first  18  or  19  miles  north  of  San  Antonio,  the  water  sup- 
plies are  obtained  chiefly  from  the  Georgetown-Edwards  limestones, 
which  are  reached  at  depths  varying  from  600  to  700  feet  in  San 
Antonio  to  surface  exposures  north  of  the  north  fork  of  Salado 
Creek.  Beyond  about  19  miles  from  San  Antonio,  the  wells  enter 
the  Glenrose-Travis  Peak  formations. 

Bulverde  Road:  The  Bulverde  Road  passes  northeast  from  San 

Antonio  to  Wetmore,  thence  approximately  north  to  the  county  line. 
From  the  courthouse  to  the  north  city  limits,  this  road  lies  in  the 
valley  of  San  Antonio  Creek.  Near  the  north  city  limits  it  crosses 
the  zone  of  faulting  elsewhere  described  and  passes  onto  exposures 
of  the  Austin  formation.  At  the  north  side  of  the  road  about  6 % 
miles  from  San  Antonio  is  a deep  sink  hole  in  the  Austin  chalk. 
From  Wetmore  to  the  top  of  the  range  of  hills  1 V2  miles  north,  the 
road  again  crosses  the  Austin  exposures.  At  the  north  slope  of 
this  hill,  as  already  noted,  are  exposures  of  the  Eagleford  and 
Austin  formations,  beyond  which  are  the  hills  of  the  Georgetown- 
Edwards  formations.  The'  Glenrose-Edwards  contact  is  apparently 
crossed  about  211/£  miles  from  San  Antonio. 

Nacogdoches  and  Austin  roads:  The  Nacogdoches  and  Austin 

roads  almost  parallel  the  structural  lines  in  this  county.  The  Nacog- 
doches road  which  branches  from  the  Bulverde  Road  one  mile 
south  of  Wetmore  affords  exposures  of  the  Austin  formation.  The 
Austin  road  lies  toward  the  south  side  of  the  structurally  high  area 
described  as  the  San  Antonio  structure.  From  the  county  line  at 
Selma  to  Salado  Creek  the  exposures  seen  on  this  road  are  chiefly, 
if  not  entirely,  those  of  the  Austin  formation.  Beyond  the  valley  of 


92 


University  of  Texas  Bulletin 


Salado  Creek  to  the  city  limits  are  exposures  some  of  which  may 
represent  the  Taylor  formation. 

St.  Hedwig  Road:  The  St.  Hed.wig  Road  runs  about  due  east 

from' San  Antonio.  In  the  eastern  part  of  San  Antonio  this  road 
crosses  the  high  gravel  deposits  mapped  as  the  Uvalde  formation. 
The  valley  of  the  Salado  at  this  crossing  includes  alluvial  deposits 
referred  to  the  late  Pleistocene  flood-plain.  About  % mile 
east  of  the  crossing  on  Salado  Creek  the  road  ascends  a pro- 
nounced terrace  and  passes  onto  the  very  level  plain  referred  to  the 
Leona  formation,  which  continues  to  the  break  to  Rosillo  Creek, 
where  exposures  are  seen  of  the  Midway  formation.  The  gravels 
of  this  formation  as  seen  in  the  exposures  on  this  terrace  are  largely 
pisolitic.  Prom  Rosillo  Creek  to  the  east  county  line  the  exposures 
on  this  road  are  interpreted  as  representing  the  Tertiary  forma- 
tions. The  contact  line  between  the  Midway  and  Wilcox  formations 
is  placed  about  14  miles  from  San  Antonio. 

Pleasanton  Road:  The  Pleasanton  Road  runs  about  due  south 

from  San  Antonio.  For  the  first  six  miles  from  San  Antonio  this 
road  passes  over  the  level  plain  of  the  Leona  formation.  The 
gravels  of  this  formation  east  of  the  Pleasanton  Road  near  the  San 
Antonio  River  are  chiefly  pisolitic,  while  west  of  this  road  they  are 
largely  flint  pebbles  deposits.  The  formations  underlying  the  plain 
as  indicated  by  well  records  are  the  Taylor  and  Navarro,  with  prob- 
ably more  or  less  of  the  Tertiary  toward  the  southern  part  of  the 
plain.  About  seven  miles  from  San  Antonio  the  road  passes  onto 
the  Midway  formation.  Near  the  Alta  Vista  oil  field,  about  8 V2 
miles  from  San  Antonio,  is  the  fault  in  the  Tertiary  formations  to 
which  reference  has  been  made.  From  near  Mitchell’s  Lake  to  about 
three  miles  beyond  the  Medina  River,  the  exposures  on  this  road 
are  mapped  as  Wilcox.  Within  about  4 miles  of  the  county  line,  the 
road  enters  the  belt  of  sand  hills  representing  the  Carrizo  formation. 

Somerset  Road:  The  Somerset  Road  runs  in  a general  south- 

west direction  from  San  Antonio  into  Atascosa  County.  From  San 
Antonio  to  Leon  Creek  the  road  passes  over  the  Pleistocene  plain 
(Leona  formation).  The  surface  elevation  rises  very  gradually  to 
near  the  middle  of  the  plain,  and  again  drops  gradually  toward 
Leon  Creek.  Near  this  creek,  the  road  descends  to  a lower  plain 
forming  a well  marked  terrace.  Flowing  artesian  water  is  obtained 
on  this  road  from  the  Georgetown-Edwards  limestones  which  are 
reached  at  a depth  of  from  900  to  1000  feet,  the  top  of  the  Coman- 
chean  being  reached  at  about  850  to  900  feet.  However,  the  water 
from  these  formations,  from  about  six  or  seven  miles  from  San  Anto- 
nio on  to  the  southwest  as  far  as  tests  have  been  made,  is  a warm 
sulphur  water  not  desirable  for  drinking  purposes,  although  used 


Geology  and  Mineral  Resources  of  Bexar  County  93 

to  some  extent  for  irrigation.  From  Leon  Creek  to  the  Medina 
River  is  a plain  which  is  gravel-covered.  The  timber  growth  is 
chieflly  mesquite.  In  the  bed  of  the  Medina  River  are  seen  large 
concretions  of  the  Tertiary  formations.  The  late  terrace  deposits  of 
the  Medina  River  valley  at  this  crossing  have  a thickness  of  as 
much  as  50  feet.  They  consist  of  loams  in  which  are  found  many 
land  snails,  chiefly  Bulimuliis.  On  the  south  side  of  the  Medina, 
this  plain  continues  for  about  one  mile,  beyond  which  to  the  county 
line  the  road  passes  over  the  Tertiary.  Beyond  Somerset  are  sev- 
eral exposures  of  thinly  laminated  sands  of  the  Wilcox  formation. 

Pearsall  (Frio)  Road:  The  Pearsall  Road  runs  southwest  from 

San  Antonio.  From  San  Antonio  to  Leon  Creek  this  road  leads 
across  the  level  plain  on  which  Kelly,  Field  is  located,  mapped  as 
the  Leona  formation.  The  gravel,  silt,  and  loam  deposits  of  this 
plain  have  a depth  of  from  25  to  50  feet  and  are  utilized  in  places 
for  road  material.  The  native  vegetation,  now  largely  cleared,  is 
mesquite.  The  formation  underlying  the  plain  is  probably  chiefly 
Navarro  as  indicated  by  exposures  on  Leon  Creek.  The  Coman- 
chean  is  reached  in  wells  drilled  in  this  plain  on  the  Pearsall  Road 
at  between  900  and  950  feet,  being  one  or  two  hundred  feet  nearer 
the  surface  here  than  on  the  CastroviUe  Road  two  or  three  miles 
northwest.  This  difference  is  due  to  structural  features  elsewhere 
described.  Artesian  water  is  obtained  in  these  deep  wells  from  the 
Georgetown-Edwards  formations  which  are  reached  at  about  1050 
feet,  and  are  penetrated  in  drilling  a variable  depth.  In  some  of 
the  wells  on  the  lower  lands  the  artesian  water  flows  at  the  surface, 
although  in  wells  located  on  higher  lands  the  water  is  non-flowing. 

In  the  bluffs  of  Leon  Creek  at  the  Pearsall  Road  crossing  are  ex- 
posures of  the  Navarro  formation  elsewhere  described.  From  Leon 
to  Medina  Creek  the  road  passes  over  rolling  lands  with  gravelly 
soils  indicating  remnants  of  flood-plain  deposits.  The  underlying 
formation  is  largely  concealed  but  is  probably  the  Navarro  forma- 
tion. From  Media  Creek  to  the  Medina  River,  on  this  road,  is  a 
late  Pleistocene  flood-plain  deposit,  mapped  as  the  Medina  flood- 
plain.  From  the  Medina  River  to  the  county  line,  this  road  passes 
over  the  Tertiary  probably  chiefly,  or  entirely,  on  the  Wilcox  forma- 
tion. In  the  cut  in  the  public  road  west  of  the  Medina,  are  ex- 
posures of  the  Wilcox  already  described. 

Castroville  Road:  The  Castroville  Road  (West  Commerce  Street, 

in  San  Antonio)  passes  to  the  south  of  the  termination  of  the 
range  of  Austin  Hills,  originating  in  San  Antonio.  By  turning  north 
on  Zalzamora  Street,  a distance  of  about  one-half  mile,  an  exposure 
of  the  upper  part  of  the  Austin  formation  may  be  seen.  On  the 
other  hand,  by  turning  south  on  West  19th  Street  an  exposure  of 
what  is  probably  the  Taylor  formation  may  be  seen  near  the  east 


94 


University  of  Texas  Bulletin 


end  of  Elmendorf  Lake.  After  passing  Elmendorf  Lake  the 
road  goes  onto  a level  plain  representing  the  Leona  formation, 
which  continues  to  Leon  Creek.  Well  records  indicate  that  the 
base  of  the  Upper  Cretaceous  lies  at  a depth  of  between  1050  and 
1100  feet  from  the  surface.  Hence,  as  the  flood-plain  deposits  are 
only  from  25  to  50  feet  deep,  the  formation  on  this  part  of  the 
plain , next  below  the  Pleistocene  is  probably  the  Navarro.  Water 
is  obtained  on  this  plain  from  shallow  wells  entering  the  Pleistocene 
and  from  deep  wells  entering  the  Comanchean  formations.  The 
deep  wells  give  artesian  water,  which  rises  to  within  from  25  to  50 
feet  of  the  surface,  depending  upon  the  elevation  at  the  well.  Near 
Leon  Creek  the  road  passes  down  to  a lower  and  later  small  terrace 
bordering  the  present  stream.  The  gravels  of  this  late  terrace  and 
of  the  stream  bed  are  used  in  road  construction. 

At  the  Leon  Creek  crossing  on  this  road  are  seen  exposures  of  the 
Navarro  formation  elsewhere  described.  Beyond  the  creek  the  road 
passes  onto  the  high  terrace  mapped  as  Uvalde  formation.  From 
Leon  Creek  to  Media  Creek  the  exposures  are  chiefly  of  these  high 
terrace  deposits.  This  formation,  however,  is  thin  and  small  streams 
have  cut  through  in  places  to  the  underlying  clays,  probably  of  the 
Navarro  formation,  as  indicated  by  an  exposure  seen  in  a small 
stream  channel  about  one  mile  beyond  Leon  Creek  in  which  many 
Exogyra  costata  are  found.  The  timber  growth  of  this  upland  is 
chiefly  mesquite  with  some  oak  on  lands  underlaid  by  caliche-ce- 
mented terrace  gravels.  The  water  supply  here  is  chiefly  from  deep 
wells  entering  the  Comanchean  limestones.  The  top  of  the  Coman- 
chean on  this  plain  is  reached  at  a depth  of  about  575  feet  and  the 
water-bearing  limestones  at  about  700  feet  from  the  surface.  (Well 
of  A.  Skolout). 

From  Media  Creek  to  the  county  line  this  road  passes  over  an 
undulating  country  in  which  the  chief  timber  growth  is  mesquite, 
and  which  is  underlaid  throughout  probably  by  the  Navarro  forma- 
tion. At  the  surface  are  found  remnants  of  gravel  terrace  deposits 
which  were  formerly  perhaps  extensive,  having  been  largely  re- 
moved by  erosion.  Turning  south  on  the  Cagnon  cross  road  about 
one  mile  there  is  seen  at  the  slope  to  the  valley  of  the  Medina 
River  an  exposure  of  yellow  clay  containing  many  Exogyra  costata. 
To  the  north  of  the  Castroville  Road  and  near  the  Cagnon  cross 
road  is  the  fuller’s  earth  plant  elsewhere  described.  To  the  north 
from  this  road,  near  the  west  line  of  the  county,  may  be  seen  tbe 
pronounced  range  of  Austin  Hills  while  to  the  south  a few  miles  is 
seen  the  broad  valley  of  the  Medina  River.  One  of  the  lines  of 
heavy  faulting  approximately  parallels  this  road  from  near  the 
Leon  Creek  crossing  to  the  county  line  separating  the  dissected  plain 
over  which  the  road  passes  from  the  Austin  Hills  to  the  north. 

Potranca  Road:  From  Leon  Creek  to  the  west  county  line,  the 


Geology  and  Mineral  Resources  of  Bexar  County  95 

Potranca  Road  lacks  but  little  of  paralleling  the  structural  lines  of 
the  Cretaceous  formations.  The  road  runs  a few  degrees  south  of 
west  while  the  lines  of  structure  are  more  nearly  due  southwest. 
For  somewhat  less  than  a mile  beyond  Leon  Creek  the  road  leads 
across  a hill  formed  of  Austin  chalk.  Beyond,  for  about  one  and 
a half  miles,  is  a broad  valley  covered  by  gravel  deposits.  Although 
not  shown  on  the  map,  this  terrace  plain  extends  north  to  Culebra 
Creek  and  possibly  represents  the  location  of  a former  valley.  From 
this  valley  to  the  county  line  the  road  lies  continuously  on  the 
Upper  Cretaceous  formations  with  frequent  exposures.  For  the 
most  part  the  soft  marly  phases  of  the  Austin  are  represented,  the 
•oyster.  Exogyra  ponderosa  being  very  abundant,  although  at  the 
Media  Creek  crossing  and  at  several  places  beyond  there  are  seen 
the  hard  limestones  of  the  Austin  formation.  The  vegetation  in- 
cludes a dense  growth  of  live  oak  on  many  of  the  hills,  and  mes- 
quite  in  the  valleys. 

Culebra  Road:  The  Culebra  Road  extends  northwest  from  San 

Antonio.  On  this  road  5.4  miles  from  San  Antonio,  exposures  are 
seen  at  the  south  of  the  road  containing  Exagyra  costata,  probably 
indicating  the  Navarro  formation.  At  the  Zalzamora  Creek  crossing 
are  seen  exposures  of  the  Austin  formation,  while  at  a somewhat 
higher  level  on  the  hill  slope  facing  the  valley  of  Leon  Creek  is  an 
exposure  8.7  miles  out,  interpreted  as  representing  the  Taylor 
formation.  Beyond  the  Leon  Creek  crossing  for  about  8 miles, 
aside  from  surface  materials,  the  underlying  formation  is  the  Austin 
chalk.  In  this  part  of  its  course  the  road  passes  over  the  struc- 
turally high  /area  elsewhere  described.  For  the  last  3 or  4 miles 
before  reaching  the  county  line,  the  road  passes  over  a high  gravel- 
surfaced plain,  underlaid,  as  indicated  by  well  records,  by  the 
Taylor  formation. 

The  Bandera  Road:  This  road  extends  northwest  from  San  An- 

tonio. In  a stream  bed  % mile  north  of  the  Bandera  Road,  5 miles 
from  San  Antonio,  is  an  exposure  of  yellow  clay  containing  E.  pon- 
derosa, probably  representing  the  Taylor  formation.  From  6.6  miles 
to  about  13.6  miles,  the  exposures  on  this  road  aside  from  surface 
materials  are  those  of  the  Austin  formation.  At  the  Leon  Creek 
crossing  are  the  bluffs  of  this  formation  with  an  abundance  of  fos- 
sils to  which  reference  has  previously  been  made.  From  13.6  to 
about  15  miles  is  relatively  level  land  in  which  are  occasional  ex- 
posures of  the  Buda  limestone,  the  Eagleford  shales  being  ob- 
scured. At  15.5  miles,  the  Del  Rio  is  seen  exposed  at  a pond  in  a 
stream  bed  M mile  north  of  the  road;  this  formation  is  again  seen 
near  Helotes  Creek.  At  the  Helotes  Creek  crossing  the  Edwards 
formation  lies  at  the  surface,  while  beyond  this  crossing  the  road 
passes  over  the  Glenrose  formation  to  the  county  line.  The  large 


96.  University  of  Texas  Bulletin 

fault  of  the  Baleones  fault  zone  is  crossed  on  this  road  at  Helotes 
Creek. 

Babcock  Road:  Although  lying  close  to  and  paralleling  the  Ban- 

dera and  Fredericksburg  roads,  the  Babcock  Road  affords  a few 
exposures  that  should  be  mentioned.  At  5.4  miles  from  San  An- 
tonio on  a small  tributary  to  Martinez  Creek  is  seen  an  exposure 
of  yellow  clay  containing  E.  ponderosa  and  probably  representing 
the  Taylor  formation.  From  5.8  miles  to  10  miles  the  exposures 
aside  from  surface  materials  are  chiefly  those  of  the  upper  part  of 
the  Austin  formation,  including  possibly  some  exposures  of  the 
lower  part  of  the  Taylor  formation.  The  hard  limestones  repre- 
senting the  lower  part  of  the  Austin  are  first  seen  on  this  road  10.7 
miles  from  San  Antonio.  The  Eagleford  and  Buda  formations  are 
first  seen  on  a small  stream  11  miles  out.  The  Del  Rio  is  first 
seen  on  this  road  about  12  miles  from  San  Antonio,  and  from  12  to 
13  miles  the  road  passes  over  repeated  exposures  of  the  Buda  and 
Del  Rio  formations,  the  alternating  exposures  being  due  apparently 
chiefly  to  small  faulting.  At  the  Leon  Creek  crossing  on  this  road 
is  seen  the  flint-bearing  phase  of  the  Edwards  formation.  Beyond 
the  crossing  for  a mile  or  so  the  Del  Rio  continues  to  be  seen 
occasionally  and  is  used  in  the  construction  of  a pond  near  the 
Hausman  cross  road  14.8  miles  from  San  Antonio.  The  limestone 
hills  of  the  Edwards  formation  where  crossed  by  this  road  are  two 
or  three  miles  wide,  beyond  which  the  road  passes  onto  the  Glen- 
rose  formation. 

Fredericksburg  Road:  From  San  Antonio  the  Fredericksburg 

Road  runs  west  of  north  to  the  county  line,  and  thence  to  Fred- 
ericksburg. Within  the  city  of  San  Antonio,  at  a distance  of  from 
1.5  to  2.5  miles  from  the  court-house,  this  road  crosses  the  struc- 
turally high  area  elsewhere  described  as  the  San  Antonio  structure. 
Although  not  seen  immediately  on  this  road,  Austin  exposures  have 
been  seen  both  north  and  south  of  the  road.  A cut  in  the  public 
road  at  a stream  crossing  about  one  mile  from  the  north  city 
limits  affords  an  exposure  of  yellow  clay  in  which  no  fossils  were 
found  but  which  on  lithologic  appearance  would  seem  to  represent 
the  Taylor  formation.  Beyond  this  stream  for  several  miles  is  a 
broad  valley  the  surface  of  which  is  gravel  covered.  This  valley 
is  probably  underlaid  by  either  the  TaylQr  or  the  Austin  formation. 
From  5.4  miles  to  9.3  miles,  the  exposures,  except  those  of  the 
Uvalde  gravels,  are  interpreted  as  representing  the  Austin  forma- 
tion. From  9.3  to  9.7  miles  are  exposures  of  yellow  clays  contain- 
ing E.  ponderosa,  apparently  representing  the  Taylor  formation. 
From  9.7  to  10  miles  exposures  of  the  Austin  formation  are  con- 
tinuous. The  hard  limestones  of  the  lower  part  of  the  Austin 
are  first  see.n  on  this  road  at  10  miles  from  San  Antonio,  where 


Geology  and  Mineral  Resources  of  Bexar  County  97 

they  are  underlaid  by  the  Eagleford  shales.  From  10  miles  to  13 
miles  from  San  Antonio  this  road  crosses  the  belt  of  repeated  ex- 
posures of  the  Buda  and  Del  Rio  and  other  formations  to  which 
reference  has  already  been  made,  the  succession  of  exposures  being 
due  in  part  to  small  faulting  and  in  part  to  folding.  At  the  Leon 
Greek  crossing  and  for  a mile  or  so  beyond  exposures  are  seen  of 
the  Edwards  formation.  About  16  miles  from  San  Antonio  the 
road  passes  onto  the  Glenrose  formation  and  continues  chiefly  or 
entirely  on  that  formation  to  the  county  line. 

ECONOMIC  GEOLOGY 

The  mineral  resources  of  Bexar  County  include  artesian  and 
other  ground  waters,  cement,  concrete,  clay,  fuller’s  earth, 
greensand,  lignite,  limestone,  petroleum,  natural  gas,  and  road 
materials.  On  the  accompanying  map  is  shown  the  location  of 
some  of  the  principal  mineral  deposits  of  the  county  (Fig.  6). 

ARTESIAN  AND  OTHER  UNDERGROUND  WATER  SUPPLIES 

The  underground  waters  are  one  of  the  very  valuable  natural 
resources  of  Bexar  County.  In  parts  of  the  county  flowing 
artesian  wells  of  large  volume  are  secured.  In  some  other  areas 
non-flowing  waters  are  secured  from  wells  of  moderate  depth ; 
while  in  some  limited  areas  difficulty  has  been  met  with  in  secur- 
ing sufficient  water.  The  relation  of  the  geology  to  the  water 
supply  is  very  close,  some  of  the  formations  containing  but 
little  water,  while  others  afford  an  abundant  supply.  The 
principal  water-bearing  formations  are  the  Glenrose-Travis  Peak 
limestones,  the  Georgetown-Edwards  limestones,  the  limestones 
of  the  Austin  formation,  and  the  sands  and  sandstones  of  the 
Tertiary  formations.  The  formations  in  which  the  water  supply 
is  frequently  found  to  be  limited  are  the  Del  Rio,  Buda,  Eagle- 
ford,  Taylor,  and  Navarro,  and  the  upper  part  of  the  Austin  in 
which  the  rocks  are  of  such  close  texture  as  to  retain  and 
yield  very  little  water.  Since  the  formations  pass  through 
the  country,  as  already  explained,  in  belts  having  a general 
northeast-southwest  direction,  it  follows  that  the  county  divides 
itself,  with  respect  to  water  supplies,  into  similar  belts,  depend- 
ing upon  the  character  of  the  underlying  formations  reached  by 
wells. 


7-Bex. 


98 


University  of  Texas  Bulletin 


PRINCIPLES  OF  ARTESIAN  WELLS  AND  GROUND-WATER  • 
ACCUMULATION 

Since  the  principles  underlying  the  accumulation  of  ground 
waters,  including  flowing  artesian  wells,  have  been  fully  set 
forth  in  numerous  publications,  they  need  not  be  discussed 


Fig.  6.  Sketch  map  indicating  the  brick,  cement  and  fuller’s  earth 
plants,  lime  kilns,  lignite  mine,  oil  and  gas  fields  and  areas  of  flow- 
ing artesian  water. 


Geology  and  Mineral  Resources  of  Bexar  County  99 

here.  It  is  therefore  sufficient  to  state  that  for  the  coastal 
plains  area  of  this  county  the  principal  intake  area  for  the 
ground  water  is  through  the  surface  exposures  of  the  forma- 
tions on  their  outcropping  margins,  chiefly  south  of  the  Balcones 
Escarpment.  The  flowing  artesian  waters  obtained  from  the 
Georgetown-Edwards  limestones  enter  those  formations 
chiefly  within  a few  miles  of  the  Balcones  Escarpment. 

The  pores  and  cavities  in  the  rock  become  completely  filled 
with  water  up  to  limits  which  vary  appreciably  between  dry 
and  wet  seasons.  In  the  case  of  some  of  the  formations, 
especially  the  limestones  referred  to,  the  pores  and  cavaties  are 
so  numerous  that  the  quantity  of  water  contained  in  the  forma- 
tion is  very  great,  so  that  the  supply  is  not  appreciably 
affected  by  pumping. 

With  regard  to  the  artesian  waters,  the  conditions  are  ad- 
mirable for  securing  flowing  wells  from  the  water-bearing 
strata  where  the  elevation  is  not  greater  than  the  effective 
head  of  the  water.  Thus  water  entering  the  Georgetown- 
Edwards  formation  follows  the  dip  of  the  formation  through 
the  cavities  and  openings  of  the  limestones  to  a lower  level, 
and  when  tapped  by  wells  will  rise  in  the  boring.  The  height 
to  which  the  water  will  rise,  however,  varies  with  the  seasons. 
Thus,  following  a long  period  of  dry  weather  or  a succession 
of  dry  seasons,  the  water  line  has  been  known  to  drop  at  San 
Antonio  to  the  actual  level  of  659  feet  above  sea.  On  the 
other  hand,  following  extremely  wet  seasons,  the  water  has 
been  known  to  rise  to  the  level  of  694  feet  above  sea,  giving 
a maximum  recorded  variation  of  36  feet.#  As  a rule,  the 
static  head  of  the  water  varies  between  seasons  within  much 
smaller  limits.  At  San  Antonio,  the  static  head  of  the  water 
of  the  Georgetown-Edwards  formations  is  close  to  an  average 
of  670  feet  above  sea  level.  While  exact  measurements  are 
not  available,  the  water  of  these  formations  seem  to  be  under 
a very  close  approximation  to  this  same  static  head  throughout 
the  county.  The  only  departure  that  would  be  expected  from 
this  head  is  that  due  to  the  friction  of  flow  through  the  rock, 
which  apparently  is  not  great  in  this  formation. 


*Records  supplied  by  San  Antonio  Water  Supply  Company. 


100  University  of  Texas  Bulletin 

Water  obtained  from  the  Austin  formation  has  been  found 
to  be  under  a static  head  in  this  area  which  differs  more  or  less 
from  the  Edwards  formation.  Water  obtained  from  the  Travis 
Peak  formation,  where  reached  by  wells  in  the  coastal  plain, 
has  been  found  to  be  under  a greater  static  head  than  is  greater 
than  that  of  the  overlying  formations.  This  fact  is  indicated  by 
water  obtained  in  the  Waring  well,  subsequently  described  (No. 
139,  of  the  section  on  well  records). 

WATER  OF  THE  GLENROSE-TRAVIS  PEAK  LIMESTONES 

The  Glenrose  formation,  as  shown  on  the  geologic  map,  and 
as  stated  in  the  discussion  of  the  geology,  lies  at  or  near  the 
surface  in  that  part  of  the  county  north  of  the  Balcones 
escarpment.  Although  not  exposed  at  the  surface,  the  Travis 
Peak  formation  underlies  the  Glenrose  and  is  reached  by  some 
of  the  deeper  wells.  In  the  Glenrose  formation  water  is 
usually  found  in  sufficient  quantity  for  household  and  stock 
purposes  within  the  moderate  depth  of  200  or  300  feet.  A 
few  wells  Jiave  failed  to  get  water  in  the  Glenrose,  and  some 
have  obtained  a moderate  supply  by  going  through  the  Glenrose 
into  the  Travis  Peak  formation  beneath,  while  two  wells  within 
this  area,  one  on  the  Leon  Springs  Reservation  and  one  on 
Camp  Bullis  Reservation,  have  passed  entirely  through  the 
Travis  Peak  formation  without  securing  a supply  of  water 
sufficient  for  the  needs  of  the  Government  camps.  The  wells 
passing  through  these  two  formations  encountered  a succession 
of  hard  and  soft  limestones,  marls,  clays,  and  sands. 

East  of  the  Balcones  Escarpment  these  formations  pass  by 
faulting  and  dipping  to  a much  lower  level  and  are  overlaid  by 
later  formations.  At  the  Waring  estate,  about  eight  miles 
northwest  of  San  Antonio,  a deep  well  has  been  drilled 
through  the  overlying  formations,  and  into,  if  not  through 
the  Travis  Peak.  In  this  well  water  is  said  to  have  been 
obtained  at  the  depth  of  2699  feet.  This  water  is  probably 
from  sands  near  the  base  of  the  Travis  Peak,  or  the  equivalent 
of  the  Trinity  sands  farther  north.  The  water  rose  to  within 
about  46  feet  of  the  surface  or  to  about  the  actual  level  of 
874  feet  above  sea.  From  the  record  secured  in  this  well,  it 


Geology  and  Mineral  Resources  of  Bexar  County  101 

seems  probable  that  the  Travis  Peak  formation  in  this  imme- 
diate area  may  be  found  to  give  an  important  water  supply, 
the  artesian  head  of  which  is  much  higher  than  that  of  the 
later  formations. 

WATER  OF  THE  GEORGETOWN-EDWARDS  LIMESTONES 

The  Georgetown-Edwards  limestones  afford  the  largest  reser- 
voirs for  underground  waters  of  any  of  the  formations  of 
this  area.  The  surface  outcropping  of  these  formations  which 
is  their  intake  area,  forms  a relatively  narrow  belt  lying 
immediately  south  of  the  Baleones  Escarpment  and  forming  the 
line  of  hills  elsewhere  described  as  the  Edwards  Flint  hills. 
Within  the  area  in  which  these  formations  lie  at  the  surface 
they  supply  non-artesian  water  to  wells  at  the  moderate 
depth  of  from  100  to  300  feet.  Farther  to  the  south  and  south- 
east these  limestones  pass  under  later  impervious  formations 
and  the  cavities  of  the  limestones,  becoming  filled,  contain  very 
large  quantities  of  water,  which  by  reason  of  the  eastward 
dip  of  the  formations  is  under  pressure  and  hence  becomes  ar- 
tesian water. 

AREA  OF  ARTESIAN  FLOW 

The  area  of  flowing  wells  from  the  Georgetown-Edwards  lime- 
stones is  indicated  on  the  accompanying  map  (Fig.  6).  Toward 
the  north  the  flowing  area  is  limited  by  the  increased  elevation 
of  the  country,  the  land  rising  to  a level  higher  than  the  static 
head  of  the  artesian  water.  To  the  south,  on  the  other  hand,  the 
limitation  of  this  belt  for  practical  purposes  is  due  in  part  to 
the  increased  depth  of  the  water-bearing  formations,  but  more 
particularly  to  a change  in  the  quality  of  the  water.  South  of 
the  area  indicated  on  the  map,  the  water  of  these  formations  con- 
tains hydrogen  sulphide  gas,  and  also  increases  notably  in  tem- 
perature, becoming  a warm  sulphur  water.  The  amount  of  salts 
in  solution  likewise  increases  until  the  water  becomes  undesir- 
able for  household  use. 

WELLS  LOCATED  IN  THE  AREA  OF  SURFACE  EXPOSURES  OF  THE 
GEORGETOWN-EDWARDS  FORMATION 

Wells  located  immediately  south  of  the  Baleones  main  fault 
line  and  within  the  area  of  surface  exposures  of  the  Georgetown- 


102 


University  of  Texas  Bulletin  . 


Edwards  formations  encounter  in  drilling  chiefly  hard  lime- 
stones, with,  in  places,  layers  or  masses  of  flint.  Records  of 
several  wells  within  this  area  have  been  obtained  in  which  the 
depth  varies  from  100  to  about  300  feet.  The  water  obtained 
is  usually  sufficient  to  supply  household  and  ranch  purposes. 
The  Government  test  well  on  the  Bacon  Ranch  in  the  Camp 
Bullis  Reservation  passed  entirely  through  these  limestones  as 
well  as  the  Glenrose  and  Travis  Peak  formations  beneath,  with- 
out getting  sufficient  water  to  supply  the  Government  camps. 

NON  FLOWING  ARTESIAN  WELLS  OF  THE  GEORGETOWN -EDWARDS 

FORMATIONS’ 

Immediately  north  of  the  belt  of  flowing  artesian  wells  is  an- 
other belt  in  which  artesian  water  is  obtained  from  those  forma- 
tions, but  in  which  it  is  non-flowing  because  of  the  increased 
elevation  of  the  ground.  Since  this  belt  of  country  lies  to  the 
north  of  the  flowing  artesian  belt  and  hence  nearer  the  surface 
outcropping  of  the  formations  the  formations  are  reached  and 
the  artesian  water  obtained  at  a more  shallow  depth  than  farther 
south. 

FLOWING  ARTESIAN  WELLS'  OF  THE  GEORGETOWN-EDWARDS 

FORMATIONS 

The  number  of  flowing  wells  within  the  artesian  belt  ob- 
taining water  from  the  Edwards  and  Georgetown  limestones  is 
so  large  that  it  is  impracticable  to  record  more  than  a relatively 
small  number  of  them.  The  succession  of  formations  in  these 
wells,  however,  is  very  definite  and  by  reference  to  the  map 
a reasonably  definite  idea  may  be  obtained  of  the  formations 
to  be  expected  in  drilling  in  any  part  of  the  flowing  area. 
Most  of  this  flowing  area  lies  within  the  natural  divisions  of 
the  county  designated  as  stream  terrace  deposits  and  Taylor- 
Navarro  Plain  (Fig.  2).  The  succession  of  formations  to  be 
expected  in  a well  within  this  area  therefore  is  about  as 
follows  trorn  the  surface  to  the  artesian  water  horizon.- 

1.  Surface  materials,  soils,  gravel,  and  other  terrace  deposits, 
variable,  although  of  moderate  thickness. 

2.  Clays,  marls,  and  shales  representing  either  the  Taylor  forma- 


Geology  and  Mineral  Resources  of  Bexar  County  103 

tion  or  the  combined  Navarro  and  Taylor  formations;  thickness 
variable  with  the  location  from  a few  hundred  to  one  thousand  or 
more  feet. 

3.  Soft  marl  and  chalk  beds  passing  below  into  harder  lime- 
stones representing  the  Austin  formation;  thickness,  between  300 
and  400  feet.  Some  of  the  light-colored  limestones  near  the  middle 
of  this  formation  are  called  “magnesian”  by  the  drillers  in  this 
county.  The  limestones  near  the  base  of  the  formation  are  often 
quite  indurated.  Some  water  usually  containihg  more  or  less  hy- 
drogen sulphide  gas  is  often  obtained  in  the  Austin  formation. 

4.  Dark  colored  calcareous  shales,  more  or  less  sticky  in  drilling, 
representing  the  Eagleford  formation,  and  commonly  known  in 
this  county  as  the  “lignite”  or  as  the  “first  mud;”  thickness  from 
30  to  40  feet. 

5.  A uniformly  very  hard  limestone  often  characterized  by  black 
specks,  representing  the  Buda  formation;  thickness  quite  uniformly 
from  60  to  65  feet. 

6.  Clay  usually  blue  or  yellow  in  color  and  often  containing 
small  twisted  “ram’s  horn”  shells;  thickness  in  this  county  qidte 
uniformly  from  65  to  70  feet.  This  formation,  the  Del  Rio  clay,  is 
very  generally  referred  to  by  the  drillers  as  the  “mud  hole”  or  as. 
the  “big  mud”  or  as  the  “second  mud.” 

7.  The  Georgetown  and  Edwards  limestones  lie  immediately  be- 
neath the  clays  of  the  Del  Rio  formation.  After  reaching  the  lime- 
stone the  drilling  is  continued  until  a sufficient  quantity  of  water  is 
obtained.  In  some  wells  the  drilling  is  continued  into  these  forma- 
tions for  only  a few  feet  while  in  other  wells  it  is  continued  to  a 
considerable  depth.  In  general,  it  is  reported  that  the  amount  of 
water  secured  is  increased  with  increased  depth  in  these  formations. 

WATER  OF  THE  DEL  RIO  AND  BUDA  FORMATIONS 

The  Del  Rio  and  Buda  formations  supply  relatively  little 
water.  The  Del  Rio  consists  of  clays  chiefly  while  the  Buda  is 
a close-grained  limestone,  neither  being  sufficiently  porous  to  be 
well  adapted  as  water  reservoirs.  A few  strong  flowing  wells 
are  reported  as  terminating  in  the  Buda  formation.  Probably, 
however,  in  these  instances  the  drill  enters  fracture  zones  in 
the  rock,  the  water  obtained  being  derived  from  the  underlying 
water-bearing  limestones.  These  formations,  however,  par- 
ticularly the  Del  Rio,  form  the  overlying  impervious  stratum 
which  confines  the  artesian  waters  within  the  Georgetown- 
Edwards  limestones. 


104  University  of  Texas  Bulletin 

WATER  OF  THE  EAGLEFORD  AND  AUSTIN  FORMATIONS 

As  a water-bearing  rock,  the  Austin  formation  is  somewhat 
unreliable.  A considerable  number  of  wells  have  obtained 
good  water  in  moderate  quantities  from  this  formation,  but 
on  the  other  hand,  a large  number  of  wells  drilled  into  this 
formation  have  secured  water  containing  too  much  hydrogen 
sulphide  gas  to  be  desirable.  The  formation  contains  con- 
siderable quantities  of  pyrite  and  doubtless  the  hydrogen 
sulphide  in  the  water  is  incident  to  the  oxidation  of  the 
pyrite.  The  water  is  obtained  chiefly  from  the  limestones  of 
the  lower  part  of  the  formation. 

The  Eagleford  formation,  which  lies  below  the  Austin,  is 
relatively  thin  in  this  county  and  consists  of  calcareous  shales. 
It  contains  as  a rule  relatively  little  water. 

WATER  OF  THE  TAYLOR  AND  NAVARRO  FORMATIONS 

The  Taylor  and  Navarro  formations,  which  consist  chiefly 
of  compact  marls,  clays,  and  shales,  nearly  a thousand  feet  in 
thickness,  are  essentially  non-water-bearing.  Wells  drilled 
through  these  formations  in  the  Leon  Creek  gas  field,  the  Alta 
Vista  and  the  Somerset  oil  fields,  report  very  little  water  until 
within  the  middle  or  lower  part  of  the  Austin  formation.  There 
are,  therefore,  very  few  water  wells  terminating  in  these  forma- 
tions. 

WATER  OF  THE  TERTIARY  FORMATIONS 

The  sand  lenses  which  are  often  numerous  in  the  Tertiary 
formations  afford  moderate  supplies  of  good  water.  Wells 
terminating  in  these  formations  supply  water  in  sufficient 
quantities  for  household  purposes  at  Somerset,  Elmendorf,  and 
elsewhere  in  the  southern  part  of  the  county. 

For  the  record  of  numerous  wells  in  this  county,  see  the 
section  on  well  records. 

SPRINGS 

The  permanent  surface  waters  of  this  county  are  derived 
from  springs,  the  largest  springs  of  the  county  being  those  in 


Geology  and  Mineral  Resources  of  Bexar  County  105 

San  Antonio  at  the  headwaters  of  the  San  Antonio  River,  and 
on  the  Salado  River  a few  miles  east  of  San  Antonio,  and  in 
San  Pedro  Park.  These  springs  are  located  near  fault  lines 
and  without  doubt  are  supplied  from  the  underground  artesian 
reservoir,  the  water  escaping  to  the  surface  through  breaks 
in  the  rock  incident  to  faulting.  The  following  observations 
have  been  recorded,  which  seemingly  establish  the  connection 
between  the  artesian  reservoir  and  the  water  from  these 
springs : “A  few  years  ago  a series  of  stakes  was  driven  in  the 
still  waters  of  the  head  lake  (of  San  Antonio  River)  and  the 
height  of  the  water  marked  thereon.  The  artesian  wells  were 
then  all  turned  on  and  let  run  for  twenty-four  hours.  The 
level  of  the  water  in  the  head  lake  or  pond  of  the  river  had 
fallen  2 inches.  The  wells  were  then  checked  and  in  about  one 
day  the  water  in  the  head  lake  was  at  its  former  level.  Then 
again  the  artesian  wells  were  by  survey  connected  in  a system 
of  levels.  An  excavation  was  made  on  the  land  of  the  observer 
below  the  water  line.  It  was  possible  by  observing  the  height 
of  the  water  in  this  hole  to  obtain  the  height  of  water  in  any 
artesian  well  in  the  city”.* 

WARM  SULPHUR  WATER  IN  THE  COMANCHEAN 
LIMESTONES 


Numerous  wells  drilled  in  Bexar  County  have  shown  that 
from  a few  miles  south  of  San  Antonio  the  water  obtained 
from  the  Georgetown-Edwards  limestones  is  warm  sulphur 
water.  The  transition  from  non-sulphur  to  sulphur  water  in 
these  formations,  in  passing  to  the  south,  is  probably  not  as 
abrupt  as  some  of  the  well  records  seem  to  indicate.  The 
somewhat  gradual  transition  from,  the  non-sulphur  to  the 
sulphur  water  areas  is  indicated  by  the  slightly  sulphurous 
waters  of  several  wells  near  the  dividing  line  between  the  two 
areas. 

No  very  satisfactory  explanation  has  been  offered  to  ac- 
count for  this  change  from  non-sulphur  to  sulphur  water  in 
these  formations.  However,  in  passing  to  the  south  or  south- 

*The  Water  Powers  of  Texas,  by  Thofnas  U.  Taylor.  U.  S.  Geol. 
Surv.,  Water  Supply  and  Irrigation  Paper  No.  105,  p.  25,  1904. 


106 


University  of  Texas  Bulletin 


east,  the  water-bearing  formations  drop  rapidly  to  lower 
levels  and  hence  are  more  deeply  buried  beneath  the  surface 
It  is  reasonable  to  assume  also  that  there  is  less  circulation  of 
water  in  these  formations  where  deeply  buried  than  in  the 
same  formations  lying  near  the  surface,  especially  within  the 
general  region  of  the  location  of  fissure  springs  which  probably 
have  permitted  the  escape  of  water  and  consequently  circula- 
tion in  the  formations  since  as  early  at  least  as  sometime  in  the 
Pleistocene  period.  The  boundary  line  of  the  sulphur  water 
area  conforms  in  general  with  the  lines  of  structure,  and  is  ap- 
proximately coincident  with  one  of  the  lines  of  heavy  faulting. 
Increased  depth  and  increased  chemical  activity  together  with 
reduced  circulations  may  account  for  an  increased  temperature 
in  these  waters. 

SOURCE  OP  HYDROGEN  SULPHIDE  IN  UNDERGROUND  WATER 

The  probable  sources  of  the  hydrogen  sulphide  in  ground 
waters  may  be  summarized  as  follows:  The  decay  of  organic 

matter , containing  sulphur;  the  reaction  of  organic  matter  upon 
sulphides  or  sulphates ; the  reaction  of  acids  upon  sulphides ; 
the  partial  oxidation  of  sulphides. 

Hydrogen  sulphide  is  formed  during  the  decay  of  both  animal 
and  vegetable  matter,  and  is  obviously  a possible  source  of 
hydrogen  sulphide  in  underground  waters.  The  hydrogen 
sulphide  found  in  shallow  waters  in  particular  is  doubtless 
very  frequently  from  organic  sources.  Thorpe  states  that  the 
decay  of  organic  matter  in  contact  with  sulphates  results  in  the 
formation  of  H2S.#  The  reaction  in  this  case  probably  results 
from  reducing  properties  of  decaying  organic  matter,  the 
sulphates  being  first  reduced  to  sulphides  according  to  the  fol- 
lowing reaction:  Na2S04+  C2  (carbon  of  organic  matter) 
=2C02-|-Na2S.  The  sulphide  is  then  acted  upon  by  the  car- 
bonic acid  to  form  H2S  as  follows:  Na2S-f-H2C03= 

H2S+Na2C03.  The  reaction  of  organic  matter  upon  the 
suphides  is  regarded  by  Van  Hise  as  another  important  source 
of  HoS  in  underground  water.! 

The  formation  of  hydrogen  sulphide  as  a result  of  action  of 

*Dictionary  of  Chemistry,  Vol.  Ill,  p.  697,  1900. 

fA  Treatise  on  Metamorphism,  Mon.  XLVII  U.  S.  Geol.  Surv., 
p.  1112,  1904. 


Geology  and  Mineral  Resources  of  Bexar  County  107 

acids  upon  metallic  sulphides  is-  one  of  the  most  familiar  of 
laboratory  experiments.  This  suggests  the  possibility  of  the 
formation  of  this  gas  as  the  result  of  the  action  of  acids  upon 
metallic  sulphides  contained  in  the  rocks.  Sulphides,  especially 
those  of  iron,  are  widely  scattered  in  the  earth’s  crust  and  occur 
in  sufficient  quantity  to  account  for  the  formation  of  H2S  gas  in 
water.  Hydrogen  sulphide  is  a weak  acid  and  its  salts  are 
decomposed  by  a stronger  acid.  Sulphuric  and  other  mineral 
acids  should  certainly  react  upon  sulphides  liberating  H2S. 
Carbonic  acid  when  abundant  reacts  upon  alkali  sulphides  to 
produce  hydrogen  sulphide.  It  is  true  that  the  alkali  sulphides 
are  normally  not  abundant  in  the  crust  of  the  earth.  Stokes 
has  shown,  however,  that  the  reaction  of  sodium  carbonate 
within  the  earth  upon  pyrite  or  marcasite  produces  sodium 
sulphide.  The  reaction  given  by  him  is  as  follows:  8FeS2+ 
15Na2C03=4Fe203+14Na2S+Na2S203+15C02.# 

It  is  a well  known  fact  that  the  carbon  dioxide  which  unites 
with  water  to  form  carbonic  acid  is  abundant  in  the  deep 
waters,  especially  in  the  limestone  formations,  the  pressure  ex- 
isting at  considerable  depth  enabling  the  water  to  hold  great 
quantities  of  carbonic  acid.  The  series  of  reactions  given  by 
Stokes  accounts  for  the  presence  of  alkali  sulphides  , in  solution 
in  the  deep  waters.  It  may  be  added  that  all  sulphides  are 
soluble  to  some  extent  in  water,  and  in  that  condition  may  be 
acted  upon  by  carbonic  acid.t 

The  partial  oxidation  of  sulphides  is,  according  to  Van  Hise, 
a possible  additional  method  of  the  formation  of  hydrogen  sul- 
phide, the  reaction  being  as  follows  4 
3FeS2+4H20+40=Fe304+4H2S  +2S02 

The  oxidizing  processes  are  the  most  rapid. near  the  surface, 
especially  above  the  underground  water  level,  and  H2S  derived 
from  this  source  probably  supplies  relatively  shallow,  rather 
than  deep  waters. 

Since  iron  sulphide  (pyrite)  is  known  to  be  present  in  the 

*From  Van  Hise,  loc.  cit.,  p.  1107. 

flnorganic  Chemistry.  International  Library  of  Technology. 
Sec.  12,  p.  11. 

$ Inorganic  Chemistry.  International  Library  of  Technology.  Sec. 
12,  p.  1113. 


108 


University  of  Texas  Bulletin 


water-bearing  formations  it  seems  probable  that  the  hydrogen 
sulphide  of  the  deeper  formations  in  Bexar  County  is  very 
largely  from  this  source. 

CEMENT 

The  one  cement  plant  in  operation  in  this  county  at  the 
present  time  is  that  of  the  San  Antonio  Portland  Cement  Com- 
pany, located  on  the  International  and  Great  Northern  Railway 
two  miles  north  of  the  north  city  limits  of  San  Antonio,  at  the 
north  side  of  the  range  of  Austin  Hills  already  referred  to  as 
originating  at  San  Antonio  and  extending  northeast  (Fig.  2). 
The  location  appears  to  be  near  the  contact  of  the  Austin  and 
Taylor  formations.  The  materials  from  which  the  cement  is 
made  accordingly  include  the  uppermost  strata  of  the  Austin 
formation  together  with  more  clayey  material  overlying  this 
rock,  which  may  represent  the  Taylor  formation.  The  rock  of 
the  Austin  formation  is  here  of  a light  yellow  color  and  of 
medium  hardness.  Upon  partial  disintegration,  it  breaks  by 
exfoliation  and  upon  further  exposure  crumbles  to  small  frag- 
ments. The  rock  as  seen  in  the  face  of  the  quarry  is  much 
broken  by  jointing,  including  small  faulting.  The  dividing  line 
between  this  rock  and  the  more  clayey  material  above  is  distinct 
and  well  marked. 

Overlying  the  clay  and  rock  is  a surface  accumulation  of 
gravel  and  pebble  deposits.  The  gravel  overburden  is  removed 
and  the  underlying  clay  and  rock  after  being  loosened  by  blast- 
ing is  loaded  into  tram  cars  by  steam  shovel  and  in  the  case  of 
the  harder  rocks,  by  hand.  The  thickness  of  the  clay  stratum 
overlying  the  rock  probably  increases  as  the  quarry  is  worked 
back  into  the  hill.  In  practice,  however,  it  is  found  necessary 
to  use  only  a limited  amount  of  clay  mixture  with  the  rock  of 
this  locality.  The  product  of  the  quarry  is  marketed  under  the 
name  of  the  Alamo  Portland  Cement. 

An  analysis  of  the  limestone  and  clay  utilized  in  this  plant 
was  made  some  years  ago  by  the  Bureau  of  Economic  Geology 
under  the  direction  of  Dr.  W.  B.  Phillips,  and  is  recorded  on 


Geology  and  Mineral  Resources  of  Bexar  County 


109 


page  65  of  Bulletin  365  of  the 

University 

of  Texas. 

analyses  are  as  follows: 

Limestone 

Shale  (clay) 

per  cent 

per  cent 

Silica  

7.80 

55.30 

Alumina  

3.45 

13.56 

Oxide  of  iron  

*1.35 

4.50 

Lime  

46.64 

9.48 

Magnesia  

None 

Carbonic  acid  

36.65 

7.45 

Loss  on  ignition  

3.35 

8.85 

99.24 

99.14 

Formerly,  the  limestone  of  the  Austin  formation  exposed  in 
what  is  now  Brackenridge  Park  at  the  north  city  limits  of  San 
Antonio  was  utilized  in  cement  manufacture.  Remnants  of  the 
old  plant  are  still  to  be  seen,  and  the  sunken  garden  of  Bracken- 
ridge  Park  marks  the  location  of  the  pit  from  which  was  re- 
moved material  for  cement  manufacture  and  to  some  extent  for 
other  purposes,  such  as  road  material  and  ballast.  The  firm 
operating  at  this  locality,  the  Alamo  Portland  Cement  Company, 
was  the  predecessor  of  the  present  San  Antonio  Portland 
Cement  Company. 

UNDEVELOPED  PORTLAND  CEMENT  RESOURCES 

In  addition  to  the  plant  now  operating  in  Bexar  County,  it  is 
probable  that  other  localities  are  found  within  the  county  capa- 
ble of  development  for  Portland  cement  manufacture.  In  select- 
ing such  localities,  however,  it  is  important  to  give  careful 
attention  both  to  transportation  and  to  raw  materials.  The 
location  should  be  easily  within  reach  of  rail  transportation  and 
should,  of  course,  be  favorably  located  with  regard  to  raw 
materials. 

Since  in  the  manufacture  of  Portland  cement  there  are  re- 
quired both  limestone  and  clay,  it  is  essential  that  a location  for 
a plant  be  selected  where  these  ingredients  are  both  readily 
available.  Approximately  three  times  as  much  limestone  is  used 
as  clay;  or  more,  if  the  limestone  contains  clayey  impurities  as 
it  often  does.  Favorable  localities,  therefore,  are  those  in  which 
clays  and  limestones  may  be. obtained  from  the  same  pit,  such 
as  are  to  be  found  on  the  contact  line  between  limestone  and 


110 


University  of  Texas  Bulletin 


clay  formations.  One  such  contact  is  that  between  the  Austin 
and  Taylor  formations  on  which,  as  already  stated,  the  plant  of 
the  San  Antonio  Portland  Cement  Company  is  located.  By 
reference  to  the  map  showing  surface  outcroppings  of  the  for- 
mations, the  approximate  line  of  separation  between  these 
formations  may  be  located  in  the  county,  thus  Aiding  in  the 
search  for  such  favorable  localities. 

Another  geologic  horizon  worthy  of  attention  in  this  con- 
nection is  that  of  the  Del  Rio  clay  together  with  the  underlying 
Georgetown-Edwards  limestones  and  the  overlying  Buda  lime- 
stone. The  Del  Rio  clay  in  this  county  has  an  awerage  thick- 
ness of  from  65  to  70  feet.  The  Buda  limestone,  which  lies 
above  this  clay,  is  a very  close-grained,  quite  pure  limestone, 
having  a thickness  when  fully  developed  of  about  60  or  65 
feet.  The  Georgetown-Edwards  series  of  limestone  below  the 
Del  Rio  clay  has  a thickness  of  several  hundred  feet. 

The  Del  Rio  clay,  as  noted  in  the  description  of  that  forma- 
tion, contains  in  places  considerable  pyrite  and  gypsum.  In 
considering  this  clay  for  cement  manufacture  it  will  be  neces- 
sary to  make  sure  that  these  ingredients  are  not  present  at 
the  locality  selected.  Nodules  of  calcium  carbonate  such  as 
are  sometimes  present  in  this  clay  are,  according  to  Eckel*,  also 
to  be  avoided.  The  Buda  limestone  is  a dense  and  usually  very 
pure  limestone  rock,  having  a thickness  of  from  60  to  65  feet. 
Following  is  an  analysis  of  the  limestone  of  this  formation  as 
developed  in  the  Chisos  Mountains  of  Trans-Pecos  Texas.  The 
formation  as  developed  in  Bexar  County  probably  differs  to 
some  extent  from  that  used  in  this  analysis,  but  the  test  is 
nevertheless  illustrative  of  the  chemical  composition  of  the 
rock  of  this  formation. 

Analysis  of  Buda  limestone  from  the  Chisos  Mountains.  From  the 
Buda  Horizon,  one  mile  east  of  Boquillas.f 


* Cement  Materials  and  Industry  of  the  United  States.  U.  S.  Geol. 
Surv.  Bull.  243,  p.  38,  1905. 

fA  Sketch  of  the  Geology  of  the  Chisos  Country,  Brewster 
County,  Texas.  By  J.  A.  Udden,  Bull.  93,  University  of  Texas,  p. 
28,  1907. 


Per  cent 


Silica  . 
Alumina 


2.35 

.21 


Geology  and  Mineral  Resources  of  Bexar  County  111 


Per  cent 


Ferric  oxide  2 4 

Lime 53.90 

Magnesia  15 

Carbonic  acid  42.23 

Water  (hygroscopic)  18 

Water  (combined)  33 

Sulphur  • Trace 


99.59 

The  Georgetown-Edwards’  series  of  limestones  lying  beneath 
the  Del  Rio  clays  has  a combined  thickness  of  several  hundred 
feet.  The  Edwards  limestone  contains  at  some  horizons  large 
masses  and  layers  of  flint  such  as  would  render  it  undesirable 
for  cement  making.  The  upper  part  of  this  limestone  series, 
however,  probably  chiefly  in  that  part  of  the  section  represent- 
ing the  equivalent  of  the  Georgetown  formation,  contains 
relatively  little  flint.  Hence  there  is  an  opportunity  of  finding 
limestones  suitable  for  cement-making  underlying,  as  well  as 
overlying,  the  Del  Rio  clays. 

By  referring  to  the  map  it  will  be  seen  that  the  San  Antonio 
and  Aransas  Pass  Railway  crosses  the  formation  referred  to 
in  the  northern  part  of  the  county. 

Another  formation  that  should  receive  consideration  in  a 
search  for  cement  materials  is  the  Eagleford.  This  forma- 
tion, which  consists  of  calcareous  shales  with  interbedded  thin 
limestones,  lies  between  the  Buda  and  Austin  formations.  In 
Bexar  County  the  Eagleford  formation  as  already  stated  is 
but  little  developed,  having  a thickness  of  about  30  or  35  feet 
only.  Its  distribution  is  such  that  surface  exposures  /are 
numerous  in  which  this  formation  is  found  lying  upon  the 
Buda  Limestone,  or  underlying  the  hard  limestones  at  the  base 
of  the  Austin  formation.  No  chemical  analyses  of  the  Eagle- 
ford shales  of  Bexar  County  are  at  hand,  and  so  far  as  the 
writer  is  aware,  no  attempts  have  been  made  to  utilize  this 
formation  in  this  county  in  cement  manufacture.  In  Dallas 
County,  the  shales  of  this  formation  are  combined  with  the 


112 


University  of  Texas  Bulletin 


limestones  of  the  overlying  Austin  formation  in  the  manu- 
facture of  cement.* 


CLAY 


The  clays  of  Bexar  County  are  found  chiefly  in  the  Del  Rio, 
Taylor,  Navarro,  Midway  and  Wilcox  formations.  The  clays 
of  the  Del  Rio  formation  are  referred  to  under  the  discussion 
of  cement  materials.  The  clays  of  the  Midway  and  Wilcox 
formations  are  utilized  in  the  manufacture  of  building  bricks. 
The  clays  of  the  other  formations  are  undeveloped  in  this 
county. 

BUILDING  BRICK 

Three  plants  in  this  county  are  producing  building  brick. 
These  are : the  Bern  Brick  Company,  San  Antonio  ; the  Star  Clay 
Products  Company,  Elmendorf;  the  San  Antonio  Sewer  Pipe 
Works,  Saspamco. 

In  the  plant  of  the  Bern  Brick  Company  the  clay  used  is 
that  of  the  Midway  formation.  According  to  unpublished 
notes  of  C.  L.  Baker,  the  clay  of  this  pit  is  a dark  blue-gray, 
easily  slaking  clay,  carrying  much  fibrous  and  platy  selenite, 
and  weathering  light  yellowish  and  drab,  containing  large 
brown  cone-in-cone  concretions  and  small  nodules  of  limonite. 
The  fossils  recognized  were  Turrit ella  mortoni,  Venericardia, 
Volutilithes,  and  Dentalium.  The  clay  of  this  pit  is  very  sim- 
ilar to  that  exposed  in  the  cut  of  the  Missouri,  Kansas  and 
Texas  Railway  nearby.  The  bricks  made  from  this  clay  burn 
to  a light  red  color.  Up-draft  kilns  are  used,  with  mesquite 
wood  as  fuel.  The  bricks  burn  to  a light  red. 

The.  clay  used  by  the  Star  Clay  Products  Company  is  from 
the  Wilcox  formation.  The  manufacturing  plant  is  at  Elmen- 
dorf, but  the  clay  pits  are  on  the  south  side  of  the  San  Antonio 
River,  about  four  miles  from  Elmendorf,  the  clay  being  trans- 
ported from  the  pit  to  the  plant  by  aerial  tram.  The  following 
description  of  these  clays  is  from  notes  made  by  Mr.  Baker. 


*The  Geology  of  Dallas  County.  By  Ellis  W.  Shuler,  llniv.  of 
Tex.  Bull.  No.  1818,  p.  35,  1918. 


Geology  and  Mineral  Resources  of  Bexar  County 


113 

In  the  clay  pit  the  dip  (perhaps  not  greatest)  is  8°  in  the  direction 
south  20°  west.  The  Wilcox  here  consists  of  coarsely-laminated 
clayey  sands.  The  sand  is  medium-grained  and  contains  flakes  of 
muscovite,  some  layers  being  more  clayey,  while  others  are  lami- 
nated with  thin  seams  of  limonite.  The  clay  is  taken  just  as  it 
occurs  without  sorting.  The  clay  contains  many  leaf  impressions. 
Layers  of  bluish  white  clay  six  to  eight  inches  thick  occur  in  the 
upper  half  of  a fifteen  foot  section.  These  clay  layers,  if  thicker, 
would  probably  make  pottery  clay. 

The  overburden  at  the  pit  consists  of  alluvial  material  amounting 
to  from  four  to  fifteen  feet.  This  covering  is  often  cemented  with 
iron  oxide  indicating  a near  approach  to  the  Mt.  Selman  formation. 
After  removing  the  overburden  the  clay  is  plowed  and  dumped  into 
tramway  cars  and  hauled  a couple  of  hundred  feet  by  mule,  and 
then  attached  to  aerial  tramway.  Mexican  labor  is  used. 

This  company  formerly  made  jars,  crocks,  jugs,  and  flower  pots, 
both  glazed  and  unglazed,  out  of  picked  blue  clay.  At  the  present 
time  this  firm  is  making  hollow  tile  and  some  brick.  The  tile  and 
brick  are  wet-molded,  then  dried  in  kilns.  Crude  oil  is  used  for 
firing  the  kilns,  lignite  being  used  for  the  boilers. 

One  of  the  pits  of  the  San  Antonio  Sewer  Pipe  Works  is  in 
Bexar  County  near  the  south  boundary,  while  the  manufactur- 
ing plant  and  other  pits  are  just  across  the  line  in  Wilson 
County.  The  clay  used  is  from  near  the  top  of  the  Wilcox 
formation.  The  following  description  of  this  plant  is  from  the 
notes  taken  by  Mr.  Baker : 

The  overburden  ati  the  pit  in  Bexar  County  is  a cross-bedded  sand 
from  10  to  12  feet  thick.  The  upper  six  to  eight  inches  are  light 
gray,  below  which  is  found  four  feet  of  light  brick  red  sands,  while 
the  remainder  beneath  is  a light  brownish  red.  The  sands  are 
often  mottled  with  red,  the  mottling!  being  sometimes  bordered  with 
limonite  or  other  cement.  This  overburden  is  removed  by  steam 
shovel.  The  dip  in  this  pit  as  indicated  at  the  contact  between  these 
sands  and  the  underlying  clay  is  one  degree  to  the  south. 

The  total  thickness  of  the  clay  worked  at  this  pit  is  about  18  feet. 
The  clay  is  blue-drab  in  color  and  slakes  on  long  exposure  to  the 
weather.  It  weathers  in  bedding  planes  and  joint  cracks  with  a 
rusty  to  brick  red  coating  of  limonite.  It  contains  small  nodules 
of  limonite  and  stains  of  yellow  alum.  It  contains  also  many  well 
preserved  fossil  plant  impressions,  especially  leaves  of  dicotyledon- 
ous plants. 

At  the  manufacturing  plant  the  clay  from  this  pit  is  mixed  with 
sandy  clay  from  another  pit.  This  company,  which  has  been  in 


8-Bex. 


114 


University  of  Texas  Bulletin 


operation  for  twenty-two  years,  originally  made  stoneware,  but  is 
now  making  sewer  pipe,  drain  tile,  and  wall  copings.  The  beehive 
type  of  kiln  is  used.  The  clay  burns  dark  brown. 

FULLER’ S EARTH 

The  fuller’s  earth  deposits  of  Bexar  County  are  being  ex- 
ploited at  the  present  time  by  but  one  firm,  the  Medina  Fullers 
Earth  Company.  The  deposit  that  is  being  mined  is  located 
near  the  headwaters  of  a small  stream  north  of  the  Castroville 
Road  and  west  of  the  Cagnon  cross  road  about  16  miles  from 
San  Antonio.  The  plant  at  which  the  earth  is  dried,  ground, 
and  prepared  for  market  is  located  in  San  Antpnio,  the  crude 
earth  being  hauled  from  the  pit  by  trucks.  In  the  pit  at  the 
present  time  there  is  seen  an  exposure  of  as  much  as  35  feet 
of  workable  fuller’s  earth.  The  overburden  is  moderate  con- 
sisting of  a few  feet  of  soil  and  gravel. 

The  fuller’s  earth'  is  of  a light  gray  or  drab  color,  becoming 
lighter  colored  upon  drying.  Upon  fresh  fracture,  the  clay 
breaks  in  a very  characteristic  manner  which  suggests  at 
once  the  resemblance  to  the  divisions  of  shells  of  ammonoids. 
The  clay  is  seemingly  entirely  free  from  sand,  and  contains 
little  if  any  calcareous  material.  When  placed  in  water,  or 
upon  long  exposure,  the  clay  slakes  into  very  finely-divided 
material.  The  soils  derived  from  it  are  sticky,  and  with  the 
inclusion  of  organic  matter  become  dark  in  color. 

The  fuller’s  earth  beds  themselves  contain  no  fossils,  so  far 
as  observed.  Their  relation  to  the  overlying  fossil-bearing  beds 
indicates,  however,  that  they  are  either  of  the  Navarro  or 
Taylor  formations  of  the  Upper  Cretaceous.  From  the  record 
of  the  well  drilled  at  the  pit  the  place  of  the  fuller’s  earth  bed 
appears  to  be  about  600  feet  above  the  base  of  the  Upper 
Cretaceous.  Of  this  interval,  the  Eagleford  and  Austin  forma- 
tions occupy  between  335  and  400  feet.  While  the  records  are 
less  exact  than  could  be  desired,  the  fuller’s  earth  bed  of  this 
pit  is  placed  provisionally  with  the  Taylor  formation  probably 
near  its  top.  In  the  cut  at  the  entrance  to  the  plant  a short 
distance  northeast  of  the  pit  and  also  on  the  hills  near  the 
pit,  are  found  exposures  of  the  yellow  clay  containing  an 


Geology  and  Mineral  Resources  of  Bexar  County  115 

abundance  of  the  oyster  Exogyra  costata.  These  exposures 
lying  at  a slightly  higher  level  probably  indicate  the  Navarro 
formation. 

The  fuller ’s  earth  produced  by  this  company  is  crushed  into 
pieces  of  moderate  size,  not  exceeding  two  or  three  inches  in 
diameter  and  is  then  passed  through  a rotating  drying  cylinder 
to  remove  the  excess  of  moisture.  The  clay  is  then  ground 
and  sacked  for  market.  It  is  said  to  be  chiefly  used  in 
clarifying  vegetable  oils  including  cottonseed  oil,  for  which 
purpose  the  present  practice  is  to  grind  the  earth  to  pass  a 
200-mesh  sieve.  It  is  used  also  in  clarifying  lard.  Aside  from 
the  finely  ground  earth,  a part  of  the  product  is  ground  to  a 
mesh  of  16-32-60,  the  earth  of  this  grade  being  used  for  mineral 
oils. 

BENTONITE 

In  addition  to  the  fuller’s  earth  there  is  found  in  this 
county  also  in  the  Upper  Cretaceous  formations  the  material 
known  as  bentonite.  The  bentonite  deposits  of  this  county 
have  been  described  in  a circular  previously  issued  by  the 
Bureau  of  Economic  Geology,  which  for  convenience  of 
reference  is  here  reprinted.  The  circular  was  based  on  the 
work  of  Mr.  C.  L.  Baker. 

In  the  course  of  work  in  Bexar  County,  the  Bureau  of  Economic 
Geology  and  Technology  of  the  University  of  Texas  has  discovered 
a bed  of  the  peculiar  clay  called  bentonite,  heretofore  known  only 
from  Wyoming.  Bentonite  has  the  property  of  absorbing  large 
quantities  of  various  liquid  substances.  When  freshly  exposed,  it 
is  generally  light  yellowish-green  or  creamy  white  in  color  and  has 
the  appearance  of  wax.  It  often  appears  as  a joint  clay,  breaking 
with  a conchoidal  fracture  into  roughly  rectangular  blocks.  On 
surfaces  exposed  to  the  weather  the  outcrop  looks  much  like  that 
of  ordinary  clay,  so  it  is  necessary  to  dig  in  and  expose  the  fresh 
material  in  order  to  be  certain  that  bentonite  really  occurs.  Ben- 
tonite has  a soft,  soapy  feel,  has  very  little  or  no  grit,  and  is  brittle. 
Mixed  with  the  proper  amount  of  water,  it  becomes  very  plastic; 
it  differs  from  all  ordinary  clays  or  kaolins  in  being  easily  fusible 
at  moderate  heat.  When  placed  in  water  it  rapidly  swells  up  and 
slacks,  like  quicklime.  It  completely  absorbs  over  three  times  its 
weight  or  seven  times  its  volume  of  water,  and  twice  as  much  gly- 
cerin as  diatomaceous  earth  will  absorb. 


116 


University  of  Texas  Bulletin 


Bentonite  has  been  put  to  various  uses.  It  is  used  for  the  man- 
ufacture of  hoof-packing,  a dressing  for  the  inflamed  hoofs  of 
horses;  and  also  in  the  manufacture  of  the  medical  dressing,  anti- 
phlogistine.  Its  chief  use  is  to  give  body  and  weight  to  paper.  It 
is  also  used  as  soap  filler,  in  the  manufacture  of  high  grades  of  soap; 
to  dilute  powerful  drugs  in  powdered  form;  and  as  an  adulterant 
in  candy.  It  is  a good  retarder  for  use  with  the  hard  cement 
plasters  and  would  probably  make  a better  absorbent  of  glycerin 
in  the  manufacture  of  dynamite  than  the  diatomaceous  earth  now 
used  for  that  purpose.  Owing  to  its  peculiar  properties,  it  is  likely 
to  find  more  extensive  and  varied  use  in  the  future. 

Bentonite  has  so  far  been  found  in  commercial  quantities  in  two 
widely  distant  localities  in  Bexar  County.  Probably  further  work 
will  show  up  a number  of  Qther  localities  or  perhaps  a continuous 
bed  outcropping  across  the  country  in  an  east-west  direction.  G'ne 
of  the  known  localities  is  in  a long  white  bluff  on  the  east  side  of 
Lucas  Creek  about  % mile  northeast  of  the  oil  derrick  on  the  B.  F. 
Masterson  ranch,  north  of  the  Castroville  road  in  the  western  part 
of  the  county.  The  other  locality  is  on  Salitrillo  Creek  on  the  F. 
Siebold  land,  in  the  eastern  part  of  the  county.  The  bentonite  has 
been  found  in  a low  north  bank,  a short  distance  downstream  from 
the  old  road  crossing  the  Salitrillo  Creek. 

CONCRETE 

The  concrete  materials  of  Bexar  County  are  obtained  from 
the  hard  limestones,  flints,  cherts,  and  from  the  pebble  and 
boulder  deposits  of  the  stream  beds  and  valleys.  The  lime- 
stones best  adapted  for  crushing  for  concrete  are  of  the  follow- 
ing formations : the  Georgetown-Edwards  limestone  series ; the 
Buda  limestone ; the  basal  strata  of  the  Austin  Formation ; and 
the  heavy  limestone  concretions  of  the  Midway  and  Wilcox 
formations.  In  addition  there  are  certain  hard  limestone 
ledges  in  the  Glenrose  and  in  the  Eagleford  and  probably 

in  some  other  formations  that  will  serve  this  purpose.  By 

reference  to  the  map  the  general  distribution  of  the  surface 
outcroppings  of  these  formations  may  be  located. 

The  flint  and  cherts  that  may  be  used  for  concrete  are 
chiefly  those  of  the  Edwards  formation  The  'gravel  and 

boulder  deposits  of  the  stream  beds  include  material  derived 
from  the  other  formations,  especially  from  the  heavy  Coman- 
chean  limestones.  The  stream  deposits  contain  as  a rule  a 
mixed  accumulation  of  flint  and  limestone  pebbles  and 


Geology  and  Mineral  Resources  of  Bexar  County  117 

boulders.  The  deposits  of  this  kind  are  best  developed  in  the 
Recent  and  Pleistocene  stream  beds  for  several  miles  south 
of  the  Balcones  Escarpment.  In  all  the  central  and  northern 
parts  of  the  county  concrete  materials  may  be  obtained  locally 
or  at  least  by  transportation  for  no  more  than  a few  miles 

GREENSAND 

The  Navarro  formation  as  developed  in  Bexar  County  is 
characterized  by  beds  of  greensand,  the  distinguishing  feature 
of  which  is  the  presence  of  the  green-colored  mineral, 
glauconite ; a mineral  containing  a small  amount  of  potassium. 
Numerous  exposures  of  the  greensand  strata  of  this  formation 
are  found  in  the  county.  Of  these  perhaps  the  best  known  is 
an  exposure  at  the  south  bank  of  Leon  Creek  between  the 
Castroville  and  Pearsall  road  crossings.  An  analysis  of  this 
greensand  has  been  given  by  Dr.  Wm.  B.  Phillips  in  Bulletin 
365  of  the  University  of  Texas,  Page  69,  1914.  The  account 
of  this  phosphatic  greensand  deposit  given  by  Dr.  Phillips  is  as 
follows : 


On  Leon  Creek,  about  7 miles  west  of  San  Antonio,  on  the  Castro- 
ville Road,  there  is  a heavy  deposit  of  phosphatic  greensand  of  the 
following  composition: 

Per  cent 


Silica  35.18 

Alumina  5.30 

Lime  .*16.00 

Oxide  of  iron 17.25 

Magnesia  Trace 

Soda  1.39 

Potash  1.69 

Carbonic  acid  8.00 

Loss  on  ignition  10.10 

Phosphoric  acid  3.30 


98.21 


118 


University  of  Texas  Bulletin 


This  deposit  contains  rounded  phosphatic  pebbles,  from  1/8-inch 
to  ^-inch  in  diameter,  of  the  following  composition: 

f Per  cent 


Silica  7.50 

Alumina  31.03 

Oxide  of  iron  4.58 

Lime 18.08 

Carbonic  acid  4.60 

Phosphoric  acid  18.19 

Loss  on  ignition  12.60 


98.34 

The  larger  pebbles  are  not  abundant.  For  the  most  part,  the 
pebbles  are  very  small,  less  than  1-20  inch  in  diameter. 

An  examination  of  10  feet  of  this  phosphatic  green  sand  foot  by 
foot  gave  the  following  results,  from  above  downward: 

Phosphoric  acid 


Per  cent 

First  foot  3.09 

Second  foot  2.38 

Third  foot  3.22 

Fourth  foot  3.07 

Fifth  foot  4.00 

Sixth  foot  2.73 

Seventh  foot 4.32 

Eighth  foot  2.60 

Ninth  foot  3.70 

Tenth  foot  3.97 


Average  3.30 


The  total  thickness  of  the  deposit  is  about  20  feet,  and  it  sets  in 
at  from  4 to  6 feet  below  the  surface. 

Taking  the  deposit  as  a whole,  it  carries  enough  lime,  potash  and 
phosphoric  acid  to  make  it  a good  fertilizing  agent.  The  rock  is 
soft  and  easily  pulverized.  It  could  be  finely  ground  and  used  with 
distinct  advantage  on  many  farm  lands  in  south  Texas,  especially 
those  in  the  vicinity  of  San  Antonio.  With  the  exception  of  some 
“stray”  phosphate  in  Fayette  County,  the  exact  locality  of  which 
is  somewhat  uncertain,  the  phosphatic  pebbles  from  Leon  Creek 
carry  considerably  more  phosphoric  acid  than  any  other  known 
deposit  in  the  State. 

LIGNITE 

Lignite  is  found  in  commercial  quantities  in  Bexar  County- 
in  the  Wilcox  formation  of  the  Tertiary  system.  The  areal 


Geology  and  Mineral  Resources  of  Bexar  County  119 

distribution  of  the  surface  outcropping  of  this  formation  is 
indicated  in  a general  way  on  the  accompanying  map.  In 
the  well  logs,  lignite  is  frequently  reported  in  this  formation  . 
These  strata  lie  at  varying  depths  below  the  surface  and  are 
of  varying  thickness  from  one  to  several  feet.  The  individual 
lignite  beds  are  doubtless  of  relatively  local  development,  but 
the  frequency  with  which  they  are  reported  indicates  the 
possibility  of  beds  of  commercial  value  at  places  in  the  part  of 
the  county  occupied  by  the  Wilcox  formation. 

At  the  present  time,  a lignite  mine  is  being  opened  up  about 
1 y2  miles  west  of  Somerset.  The  company  operating  here  is  the 
Brackenridge  Coal  Company.  The  test  pits  indicate  a lignite 
bed  having  a thickness  of  from  5 to  9 feet,  lying  about  44  feet 
below  the  surface,  and  including  a sufficient  areal  extent  to 
justify  development.  A branch  line  is  now  being  built  to  the 
mine  from  the  Artesian  Belt  Railway. 

LIMESTONE 

The  limestone  resources  of  this  county  are  extensive.  The 
Comanchean  system  in  particular  contains  a great  succession 
of  thick  limestones,  particularly  those  of  the  Glenrose,  Ed- 
wards, Georgetown  and  Buda  formations.  In  the  Upper 
Cretaceous  the  Austin  formation  is  the  chief  limestone  member. 
The  distribution  of  these  formations  is  indicated  on  the  geo- 
logic map.  The  limestone  formations  are  crossed  by  several 
of  the  railroads,  particularly  by  the  San  Antonio  and  Aransas 
Pass  Railway  north  of  San  Antonio. 

The  limestones  suitable  for  cement  and  lime  manufacture, 
and  for  building  stone  and  road  materials  are  separately  dis- 
cussed. Another  possible  use  for  the  limestones  is  to  grind  and 
apply  to  acid  soils.  As  is  well  known  many  of  the  soils  of 

*It  is  necessary  to  distinguish  in  well  logs  between  the  term  “lig- 
nite” as  used  by  drillers  operating  in  the  central  part  of  the  county, 
and  the  same  term  as  used  by  drillers  in  the  southern  part  of  the 
county.  The  latter  refer  to  the  true  lignite  of  the  Wilcox  forma- 
tion, while  the  former  refer  to  the  dark  carbonaceous  shales  of  the 
Eagleford  formation. 


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University  of  Texas  Bulletin 


the  Gulf  Coastal  Plains  are  acid  in  reaction  and  are  benefited 
for  some  crops  by  the  application  of  ground  limestone.  For 
this  purpose  a pure  limestone  is  desirable,  thus  reducing  the 
amount  of  inert  matter  that  it  is  necessary  to  transport 

Analyses  of  the  limestones  of  the  Austin  and  Buda  formations 
have  already  been  given.  The  following  test  of  a sampie  of 
the  limestone  of  the  Edwards  formation  has  previously  been 
published  in  University  of  Texas  Bulletin  365,  p.  66,  1914: 

Analysis  of  limestone  from  San  Antonio  Lime  Company. 


Per  cent 

Silica  0.70 

Alumina  0.28 

Oxide  of  iron 0.72 

Lime 55.05 

Carbonic  acid  41.9.0 

Loss  on  ignition  2.10 


100.00 

Physical  qualities: 

Crushed  at  pounds  per  square  inch 6,66  6 

Weight  of  cubic  foot  167.60  * 

Per  cent  of  cells  by  volume . . 0.20 

Volume  of  cells  in  a hundred  parts  by  weight.  . . . 0.07 

Pounds  of  water  absorbed  per  cu.  ft 0.11 


LIME 


The  limestones  suitable  for  the  manufacture  of  lime  in  Bexar 
county  are  extensive.  The  Edwards  formation  is  a very  pure . 
calcium  carbonate  and  several  quarries  have  been  opened  in 
this  formation  for  the  manufacture  of  lime.  Owing  to  un- 
favorable labor  conditions  no  one  of  these  quarries  was  in 
actual  operation  during  1918,  although  it  is  expected  that 
this  industry  will  be  resumed  as  soon  as  conditions  will  permit. 
The  San  Antonio  Lime  Company  located  on  the  San  Antonio 
and  Aransas  Pass  Railway  14  miles  from  San  Antonio  us^  rock 
from  this  formation.  The  analysis  of  the  limestone  rock 
used  by  this  company  has  already  been  given. 

With  large  quantities  of  limestone  rock  available  for  lime 
manufacture  the  success  of  a plant  of  this  kind  will  be  de- 


Geology  and  Mineral  Resources  of  Bexar  County  121 

termined  by  the  location  with  respect  to  markets,  convenience 
and  cost  of  transportation. 

BUILDING  STONE 

The  limestones  of  the  Comanchean  system  offer  very  at- 
tractive stone  for  building,  and  are  of  service  especially  where 
conditions  are  such  that  they  can  be  used  without  being 
transported  and  great  distance.  The  Glenrose,  Edwards, 
Georgetown  and  Buda  formations  are  all  capable  of  furnishing 
desirable  building-stone.  In  the  Upper  Cretaceous  the  in- 
durated ledges  of  the  Eagleford  formation  have  been  used 
locally  for  building.  These  hard  layers  have  the  advantage 
of  uniform  thickness  The  basal  members  of  the  Austin 
formation  likewise  include  ledges  of  hard  limestone  available 
locally  for  building  purposes. 


PETROLEUM  AND  NATURAL  GAS 


Petroleum  in  Bexar  County  was  probably  first  produced  in 
commercial  quantities  from  the  Dulnig  wells  about  eight  miles 
east  of  San  Antonio.  Subsequently  oil  and  gas  have  been 
discovered  at  other  localities,  and  at  the  present  time  there 
are  perhaps  between  60  and  70  producing  wells  in  the  county. 

The  oil  has  been  obtained  chiefly  in  the  southern  part  of 
the  county,  south  and  southwest  of  San  Antonio.  Although 
somewhat  scattered,  the  producing  wells,  all  of  which  are 
small  in  production,  may  be  grouped  as  the  wells  are  now 
known  into  four  or  five  more  or  less  well  defined  fields  or 
areas.  The  location  of  these  areas  is  indicated  on  the  key  map  to 
the  resources  of  Bexar  County  (Fig.  6).  They  are  as  follows: 
Alta  Vista,  Mission,  South  Medina,  Gas  Ridge,  Somerset,  and 
some  oil  wells  southeast  and  southwest  of  the  Somerset  field. 

The  Alta  Vista  field  lies  about  eight  miles  due  south  of  San 
Antonio  on  the  west  side  of  the  Pleasanton  Road.  The  Mission 
field  lies  about  three  miles  west  of  the  Alta  Vista  field,  or  about 
twelve  miles  slightly  west  of  south  of  San  Antonio.  The  Somer- 
set field  is  near  the  Bexar-Atascosa  county  line  miles  south- 
west of  San  Antonio.  A gas  and  oil  field  lies  between  Leon 


122 


University  of  Texas  Bulletin 


and  Media  Creeks  from  eight  to  twelve  miles  southwest  of 
San  Antoni 3.  To  this  field  no  name  seems  to  have  been  applied 
although  it  is  referred  to  locally  as  the  “Gas  Ridge”.  South 
of  the  Medina  River,  three  or  four  miles  south  of  the  Mission 
field,  several  wells  have  been  brought  in  recently,  located  on 
the  Kimbley-Brown  lease  chiefly  on  the  Swearingen  property. 
A few  additional  wells  are  found  in  the  county  not  included 
within  any  one  of  the  areas  mentioned. 

At  the  present  time  (1918)  five  wells  are  producing  in  the 
Alta  Vista  field,  of  which  one  flows  and  four  are  pumped.  In 
and  near  the  old  Mission  field  there  are  about  seven  wells 
producing.  In  and  near  the  old  Somerset  field  within  Bexar 
County,  about  fifty  small  wells  are  now  producing.  All  of  the 
wells  at  present  producing  in  these  three  fields  are  small,  mak- 
ing from  two  or  three  to  five  or  six  barrels  per  day.  In  the 
Atascosa  County  extension  of  the  Somerset  field,  better  wells 
are  obtained  some  of  which  are  reported  to  make  fifteen  barrels 
or  more  per  day. 

All  of  the  wells  thus  far  obtained  in  this  county  obtain  oil 
from  the  Upper  Cretaceous  formations;  in  the  Alta  Vista  and 
Mission  fields,  from  the  Austin  formation;  and  in  the  other 
fields  chiefly  from  the  Taylor  and  Navarro  formations.  The 
oil  from  the  Austin  formation  is  a heavy  oil,  reported  to  be 
about  14  or  15  degrees  Baume,  while  that  of  the  Taylor  and 
Navarro  formations  is  much  lighter,  averaging  about  36  degrees 
Baume.  Some  of  the  oil  from  the  Somerset  wells  may  come 
from  the  Midway  formation. 

THE  ALTA  VISTA  FIELD 

The  first  showing  of  oil  in  the  Alta  Vista  field  is  said  to  have 
been  in  a well  drilled  for  water.  This  led  subsequently  to 
other  wells  being  drilled,  and  in  September,  1915,  the  Mars% 
Discovery  well  was  brought  in,  the  initial  production  of  which 
was  reported  at  the  time  to  be  as  much  as  125  barrels  per  day. 
The  impetus  given  to  drilling  by  this  and  by  subsequent  suc- 
cessful wells  led  to  very  active  development  in  this  field  for  a 
short  time.  Subsequently  the  wells  rapidly  dropped  off  in 
production. 


Geology  and  Mineral  Resources  of  Bexar  County  123 
THE  MISSION  FIELD 

The  Mission  oil  field  may  be  regarded  as  essentially  the 
southwestward  extension  of  the  Alta  Vista  field.  The  first 
well  indicating  oil  drilled  in  what  subsequently  became  known 
as  the  Mission  oil  field  is  said  to  have  been  drilled  for  water  in 
June,  1901.  This  well  showed  oil  at  the  depth  of  275  feet. 
Following  the  discovery  of  this  showing  of  oil,  drilling  was 
undertaken  in  this  field  by  Nash  and  Fitzgerald  who  finally 
completed,  in  1907,  a 2900  foot  well  on  the  Linn  farm.  This 
deep  well,  a record  of  which  is  given  under  the  section  on  well 
records,  yielded  a flow  of  sulphur  water  and  was  non-pro- 
ductive of  oil.  In  this  field  after  passing  through  showings 
of  light  oil,  heavy  oil  similar  to  that  of  the  Alta  Vista  field 
is  obtained  at  the  depth  of  about  1000  feet.  Sulphur  water 
is  encountered  below  the  heavy  oil  as  in  the  Alta  Vista  field. 

GAS  RIDGE  OIL  AND  GAS  FIELD 

The  Gas  Ridge  oil  and  gas  field  lies  west  of  L'eon  Creek  and 
north  of  the  Pearsall  (Frio)  road,  and  is  located  chiefly  on 
what  is  known  as  the  Hamilton-Sw^ain  and  Cohen  lands.  Two 
wells  were  drilled  in  this  field  some  years  previous  to  1916. 
Additional  wells  yielding  gas  and  some  oil  were  drilled  during 
1916  and  at  the  time  of  the  preparation  of  this  report  several 
additional  wells  were  being  drilled.  This  field  was  visited  in 
1916  by  Mr.  E.  L.  Porch,  Jr.,  and  the  following  extract  is  from 
the  report  made  to  the  Bureau  of  Economic  Geology  by  him  at 
that  time  on  the  new  wells  then  being  drilled  or  recently  com- 
pleted. 

These  wells  are  all  within  a few  hundred  feet  of  two  gas  wells 
which  were  drilled  here  several  years  ago.  The  gas  from  one  of 
these  wells  is 'used  as  fuel  for  the  present  work,  the  other  well  being 
connected  up  so  that  it  can  be  used  if  needed.  There  is  a third 
well,  about  a half  mile  south  of  these  two  gas  wells,  which  is  said 
to  have  also  been  a gas  well 

Sarber  well  No.  1,  in  ‘which  oil  was  first  struck,  is  located  on 
the  Hamilton-Swain  tract,  while  Sarber  No.  2 is  located  on  the  Abe 
Cohen  tract,  and  is  about  500  feet  east  of  No.  1.  Well  No.  1 was 


124 


University  of  Texas  Bulletin 


drilled  with  a standard  rig,  and  is  492  feet  deep.  No.  2 was  drilled 
with  a rotary  rig,  to  a depth  of  1035  feet. 

At  the  time  of  my  first  visit  on  Friday,  a packer  was  being  placed 
in  No.  1,  and  I could  hear  the  gas  bubbling  in  it.  No.  2 was  down 
about  1000  feet  and  was  showing  some  oil  and  gas. 

I took  a sample  of  the  oil  said  to  have  come  from  No.  1,  and 
samples  of  all  of  the  cuttings  from  known  depths.  There  was  a 
barrel  of  the  oil  near  the  derrick,  and  it  had  been  standing  some 
eighteen  hours,  but  notwithstanding  this  fact,  it  smelled  something 
like  gasoline,  and  had  a specific  gravity  of  29.1°  Baume.  The  oil 
sand  in  No.  1 is  said  to  be  22  feet  thick. 

On  the  afternoon  of  the  next  day  (Saturday)  oil  was  struck  in 
No.  2 at  a depth  of  1035  feet,  it  being  estimated  that  the  drill  pene- 
trated the  “oil  ,sand”  less  than  a foot.  On  Sunday  afternoon  I 
made  my  second  trip,  but  could  not  obtain  a sample  of  the  “oil 
sand,”  and  all  the  oil  I could  secure  was  some  skimmings  from  the 
slush  pit.  This  oil  has  a specific  gravity  of  12.8°  Baume,  and  ap- 
pears very  similar  to  the  oil  obtained  in  the  Alta  Vista  field,  which 
is  about  8 miles  southeast  of  this  field. 

These  gas  wells  were  said  to  have  had  an  initial  pressure  of 
350  lbs.  per  square  inch,  and  they  still  have  sufficient  pressure 
(judging  from  observations  of  the  one  I saw  tried)  to  shoot  a flame 
out  about  forty  feet  from  the  mouth  of  a four  inch  pipe,  with  a 
roar  that  could  probably  have  been  heard  over  a mile  away.  . . . 

The  logs  of  the  wells  in  this  field  indicate  a succession  of 
clay  shale  and  gumbo.  Chalky  rock  is  noted  in  some  of  the 
deeper  wells.  There  is  little  or  no  water  in  the  higher  forma- 
tions although  water  is  doubtless  to  be  expected  in  wells 
drilled  somewhat  deeper.  The  wells  start,  aside  from  the 
surface  materials,  in  the  Navarro  formation.  The  shallow  oil 
and  gas  with  little  doubt  comes  from  the  Taylor  formation. 
The  deeper  oil,  which  is  much  heavier  than  the  shallow  oil,  may 
come  from  the  Austin  formation.  The  gas  is  probably  from 
the  Taylor  formation  at  the  depth  of  about  800  feet. 

THE  SOMERSET  OIL  FIELD 

As  in  the  case  of  the  Alta  Vista  and  Mission  fields,  the 
Somerset  field  was  discovered  as  the  result  of  drilling  for 
water.  About  1913,  Mr.  C.  Kurz  while  drilling  for  artesian 
water  on  his  property  two  miles  east  of  Somerset  encountered 
oil  which  led  to  other  wells  being  drilled  by  himself  and  others. 


Geology  and  Mineral  Resources  of  Bexar  County  125 

The  field  in  Bexar  County  now  has  about  50  small  wells.  In 
this  field  the  oil  immediately  east  of  Somerset  is  reported  as 
being  obtained  from  hard  shale  at  from  850  to  900  feet.  South 
and  southwest  of  Somerset,  however,  the  wells  are  deeper, 
reaching  in  this  county  a maximum  of  about  1250  feet.  In 
the  extension  of  the  field  into  Atascosa  County,  somewhat 
deeper  wells  are  required  to  reach  the  producing  horizon. 

On  the  Kurz  property  boulders  are  reported  as  being  en- 
countered occasionally  to  the  depth  of  about  300  feet.  Below 
this  level  is  chiefly  shale  and  gumbo.  On  the  Witherspoon 
lease  adjoining  the  Kurz  property  similar  conditions  are  en- 
countered. The  generalized  log  of  the  wells  on  this  property 
is  given  by  Mr.  Kurz  as  follows:  Alternating  beds  of  sand 

and  rock  from  the  surface  to  the  depth  of  270  feet.  Water 
in  the  formation  at  intervals  to  about  300  feet.  Below  about 
270  or  300  feet  is  alternating  shale  and  gumbo  strata  with  little 
or  no  water. 

The  wells  on  the  Harrison  property,  Slimp  and  Davidson 
lease,  south  of  Somerset,  reach  the  producing  sand  at  about  800 
feet.  The  wells  of  the  Crosby  lease,  on  the  other  hand,  near  the 
county  line,  reach  a producing  horizon  at  the  depth  of  about 
1250  feet. 

THE  SOUTH  MEDINA  OIL  FIELD 

Several  oil  wells  were  brought  in  south  of  the  Medina  River 
during  1918  by  Kimbley  and  Brown.  These  wells  reach  the 
producing  horizon  here  at  the  depth  of  from  1250  to  1350  feet. 
The  materials  passed  through  are  indicated  by  the  logs  of  the 
wells  kindly  supplied  by  Mr.  Brown,  and  published  in  the 
chapter  on  well  records.  The  wells  start  in  the  Tertiary 
formations  and  probably  terminate  in  either  the  Navarro  or 
Taylor  formation.  In  the  Park  Oil  and  Gas  Co.  test  well,  Apple- 
white  No.  1,  located  less  than  one  mile  southeast  of  Kimbley  and 
Brown,  Swearingen  No.  4,  the  Austin  formation  appears  to  have 
been  reached  at  1896  feet  from  the  surface. 

RELATION  OF  THE  BEXAR  COUNTY  OIL  FIELDS 
TO  STRUCTURE 

In  the  Alta  Vista  field  the  producing  horizon  lies  more  than 
100  feet  nearer  the  surface  at  the  north  side  of  the  field  than 


126 


University  of  Texas  Bulletin 


at  the  south  side.  A part  and  perhaps  the  greater  part  of  this 
difference  in  elevation  is  accounted  for  by  the  small  lault  or 
abrupt  monoclinal  fold  which  passes  through  this  field  to  which 
reference  has  already  been  made.  The  following  data  on  the 
depth  to  the  producing  horizon  in  this  field  were  secured  chiefly 
from  Messrs.  Ross,  Mull  and  Raborn,  operators  and  drillers  in 
this  field. 


Wells  of  Alta  Vista  field  arranged  approximately  in  order  from 
north  to  south. 


Depth  to  Actual  level 

Name  of  well  Elev.  Prod.  Prod. 

Horizon  Horizon 

Ingram  well 615  102  0 405 

Fuchs  No.  2 615  1020  405 

Aiken  605  1020  415 

Mars  Discovery  600  1070  450 

National  Oil  Co 585  1120  585 

Busby  Well  555  1150  595 


The  most  striking  feature  of  these  records  is  the  apparent 
change  in  level  of  more  than  a hundred  feet  between  the  last 
two  wells  and  those  which  precede.  This  change  in  the  level 
of  the  producing  horizon  appears  to  be  essentially  in  the  line 
of  the  fault  already  referred  to. 

In  the  Somerset  field  the  data  .on  structure  are  unfortunately 
very  limited.  In  that  part  of  the  producing  area  lying  from 
y2  to  1%  miles  southeast  of  Somerset,  the  dip  in  the  strata 
is  pretty  definitely  shown  to  be  to  the  southeast.  On  the 
Kurz  property  near  the  Artesian  Belt  Railway  about  1%  miles 
from  Somerset,  the  dip  was  found  from  well  records  to  amount 
to  40  feet  in  about  one-third  of  a mile.  In  addition  to  a 
southeast  dip  the  structures  in  the  vicinity  of  Somerset  plunge 
to  the  southwest  as  is  indicated  by  the  increased  depth  of 
well  in  passing  from  Bexar  to  Atascosa  County. 

On  the  Swearingen  property  south  of  the  Medina  River  the 
dip  in  the  producing  horizon  in  a direction  slightly  east  of 
south,  as  shown  by  the  wells  of  the  Kimbley-Brown  lease,  is 
as  much  as  115  feet  in  a little  more  than  a mile  in  a direction 
slightly  east  of  south. 

It  is  thus  seen  that  the  producing  wells  in  the  fields  on  which 


Geology  and  Mineral  Resources  of  Bexar  County  127 

•definite  data  are  available  are  located  on  the  southeast  slope 
of  the  structures.  On  other  data  already  presented  it  is  shown 
that  these  structures  are  asymmetrical,  having  a long  south- 
east slope  and  a more  abrupt  northwest  slope  or  limb ; some  of 
the  structures  possibly  being  at  the  northwest  side  by  abrupt 
dips  or  by  dips  and  faults.  In  extending  explorations  it  ap- 
pears reasonable,  therefore,  to  anticipate  the  possibility  of 
similar  structures  with,  in  general,  a northeast-southwest  trend 
farther  to  the  southeast  from  those  already  known. 

QUALITY  OP  THE  BEXAR  COUNTY  OIL 

As  has  already  been  stated  the  oil  obtained  from  the  Austin 
formation  is  much  heavier  than  that  from  the  overlying  Taylor 
or  Navarro  formations.  The  following  gravity  tests  of  the 
Bexar  County  oils  have  been  made  at  various  times  in  the 
testing  laboratory  of  the  Bureau  of  Economic  Geology.  The 
first  three  oils  are  probably  from  the  Taylor  or  Navarro 
formations ; the  others  are  probably  from  the  Austin  formation. 
The  gravity  was  taken  at  60°  F. 

No.  1.  Crude  petroleum  from  near  Somerset,  18  miles  south  of 
San  Antonio;  gravity,  35.8  ° B. 

No.  2.  Prom  a well  at  Somerset,  Bexar  County;  gravity,  30.7  ° B. 

No.  3.  Said  to  have  come  from  Sarber  well  No.  1,  Hamilton 
Swain  Tract,  about  9 V2  miles  southwest  of  San  Antonio,  at  a depth 
of  492  feet;  gravity  29.1  ° B. 

No.  4.  Collected  from  scum  of  pit  on  H.  Cohen  Tract,  Sarber  No. 
2 well,  about  500  feet  east  from  Sarber  No.  1,  at  a depth  of  1035 
feet;  gravity,  12.1  ° B. 

No.  5.  Prom  National  Oil  Company  No.  1,  1115  feet  below  sur- 
face, in  Alta  Vista  field,  Bexar  County;  gravity,  14  ° B. 

No.  6.  From  Marr’s  No  1 well,  Bexar  County;  gravity,  14  ° B. 

No.  7.  Crude  oil  from  Kelso  well  No.  1,  8 miles  south  of  San 
Antonio;  gravity,  14  ° B. 

GENERAL  CONSIDERATIONS 

The  oil  fields  of  Bexar  County  are  located  on  structures 
which  lie  within  and  are  a part  of  the  disturbed  area  of  the 
Baleones  fault-zone,  the  structure  approximately  paralleling 


128 


University  of  Texas  Bulletin 


the  Bale  ones  Escarpment.  The  location  of  this  county  near 
the  turn  of  this  fault  zone  from  the  northeast-southwest  to 
an  east-west  direction  accounts  possibly  for  the  very  heavy 
faulting  as  well  as  for  the  southwest  plunge  of  the  structures. 
The  structurally  high  areas  appear  to  be  limited  at  either  side 
in  part  by  faults  and  in  part  by  abrupt  dips,  the  longest  slopes 
being  to  the  southeast.  It  is  probable  that  the  producing 
wells  are  located  chiefly  on  the  southeast  slope  of  the  structures. 
This  is  true  at  least  for  the  Alta  Vista,  South  Medina,  and  Som- 
ersat  fields,  the  data  on  the  Mission  and  Gas  Ridge  fields  being 
at  present  less  definite.  Production  in  this  county  is  from  the 
Upper  Cretaceous,  the  Lower  Cretaceous  not  having  been  found 
to  be  producing.  Wells  drilled  to  test  formations  below  the 
Cretaceous,  if  located  in  the  central  or  southern  part  of  the 
county,  must  expect  to  drill  through  3500  feet  or  more  of 
sediments  before  reaching  formations  older  than  the  Cretaceous. 
Near  the  Balcones  Escarpment  the  formations  next  beneath 
the  Cretaceous  have  been  found  to  be  schists.  Whether  or  not 
the  Pennsylvanian  or  other  formations  come  into  the  section 
farther  to  the  south,  between  the  Cretaceous  and  the  schists, 
has  not  been  determined.  If  wells  are  drilled  in  search  of 
production  below  the  Cretaceous,  the  more  promising  locations 
are  on  structures  as  far  removed,  the  required  drilling  depth 
being  considered,  as  practicable  from  the  Balcones  Escarpment. 
In  the  further  development  in  the  Upper  Cretaceous  and  Terti- 
ary formations  it  is  suggested  that  structures  already  known 
may  be  followed  in  their  southwest  trend,  and  that  other 
similar  structures  may  be  looked  for  to  the  south  or  south- 
east of  those  already  known. 

ROAD  MATERIALS 

The  road  materials  in  Bexar  County  include  gravel,  limestone 
rock  and  sandy  clays.  Of  these  materials  the  gravels  are 
the  most  generally  utilized,  and  are  found  in  the  stream  beds 
and  in  the  flood  plain  deposits  of  the  Leona  and  Uvalde  forma- 
tions. The  distribution  of  the  limestones  and  clays  has  already 
been  indicated. 


Geology  and  Mineral  Resources  of  Bexar  County  i29 


WELL  RECORDS 

In  this  section  will  be  found  records  of  the  wells  that  have 
been  utilized  in  making  the  contour  map  showing  structure  and 
in  describing  the  water  supply  conditions  in  the  county.  Since 
in  the  structural  map  the  key  horizon  used  is  the  Del  Rio 
formation,  the  actual  level  of  the  top  of  this  formation  is  given 
for  all  wells  as  nearly  as  this  can  be  determined  or  estimated 
from  the  well  logs.  The  wells  are  numbered  for  convenience 
of  reference  and  are  entered  according  to  the  formations  in 
which  they  terminate,  those  reaching  the  oldest  formations  be- 
ing first  listed. 

WELLS  ENTERING  THE  PRE-CRETACEOUS  FORMATIONS 

As  has  already  been  stated,  two  wells  in  this  area  enter  the 
pre-Cretaceous  formations.  The  description  of  the  cuttings 
of  these  wells  will  subsequently  be  published  by  Dr.  J.  A.  Udden 
in  connection  with  the  destription  of  samples  from  other  wells 
in  the  State.  The  two  wells  are  as  follows : 

1.  Well  on  Leon  Springs  Military  Reservation,  about  2 miles 
northeast  of  Leon  Springs  Station;  elevation  about  1156  ft.  above 
sea  level;  log  made  from  the  driller’s  records  and  submitted  to  the 
Bureau  of  Economic  Geology  by  Alexander  Deussen. 

Depth  in  feet 


Quaternary: 

Black  soil  0-  4 

Gravel  4-  15 

Glenrose: 

Yellow  limestone  15-  25 

Blue  limestone,  a little  water 25-  44 

15"  casing  set  at  44s 

Blue  clay  44-  50 

Blue  limestone  50-  5 8 

Blue  clay  58-  70 

Blue  clay  and  yellow  lime  mixed  70-  95 

Yellow  limestone  95-  125 

Blue  limestone  125-  140 

Blue  clay 140-  155 

Gray  limestone  155-  160 

Yellow  limestone  160-  180 


9 -Bex. 


130  University  of  Texas  Bulletin 

Glenrose:  Depth  in  feet 

Yellow  limestone  honey-combed  180-  109 

Blue  clay  199_  210 

Gray  limestone  210-  2 47 


When  600'  was  reached, 
water  dropped  to  300'  of  surface.  Water 
struck  at  230'  appeared  to  be  a strong  vein; 
rose  50' 


Blue  clay  247-  254 

Gray  limestone  . ...  254-  309 

Crystallized  limestone  309-  315 

Blue  limestone  •. 315-  366 

Gray  limestone  366-  375 

Hard  white  crust  limestone  375-  382 

Gray  limestone  clay  in  seams  382-  400 

Yellow  limestone  400-  433 

Blue  clay  433-  487 

Gray  limestone  487-  535 

Travis  Peak  formation: 

Dark  gray  sandstone  °535-  570 

Blue  clay  570-  620 

Blue  sandstone  620-  690 

10"  casing  set  at  about  635' 

Brown  stone  690-  708 

Blue  stone  708-  775 

Blue  clay 775-  790 

Red  clay  790-  7 92 

Brown  stone  792-  800 

Light  blue  clay  800-  842 

Red  clay  842-  847 

Blue  clay 847-  855 

Green  and  red  clay  mixed 855-  865 

Gray  stone  865-  875 

Red  clay  875-  950 

Red  clay  950-  975 

Red  sandstone  975-  985 

Gray  sandstone  985-1010 

Conglomerate  rock,  small  vein  of  water  struck 1010-1015 

Pre-Cretaceous: 

Brown  clay  1015-1045 

Slate  1045-1077 

Slate  1077-1184 

Slate  seamed  with  quartz  1184-1244 

Slate  mixed  with  quartz  1244-1305 


Geology  and  Mineral  Resources  of  Bexar  County  131 


Pre-Cretaceous:  Depth  in  feet 

Slate  and  oil  1305-1344 

Vein  opened  in  cleaning  out  well.  Water 
rose  to  280'  of  surface 

Slate  mixed  with  quartz  1344-1645 

At  1645',  casing  reduced  from  8"  to  6". 

Slate  mixed  with  quartz *. 1645-203  5 

At  1728',  8"  casing  from  surface 

Slate 2035-2500 

No  water.  6"  casing 


2.  Well  on  Camp  Bullis  Reservation,  east  of  S.  A.  P.  Ry.,  about 
14  miles  northwest  of  San  Antonio.  Benkendorfer,  driller.  Eleva- 
tion, about  1050  feet.  Record  based  on  examination  of  samples  by 
Dr.  J.  A.  Udden  and  V.  V.  Waite. 

The  surface  exposure  at  the  well  shows  remnants  of  the  Buda 
limestone  underlaid  by  the  Del  Rio  clay  which  is  recognized  as  ex- 
tending to  a depth  of  53  feet.  Beneath  the  Del  Rio  is  found  the 
thick  series  of  Comanchean  limestone  including  presumably  the 
Georgetown,  Edwards,  Comanche  Peak,  Walnut  clays,  Glenrose, 
Travis  Peak  and  Basement  sands.  The  Glepros^,ins^LD^bj4«44na  was 
recognized  in  samples  from  584  feet  and  deeper,  indicating  that  the 
Georgetown,  Edwards,  and  Comanche  Peak  formations  are  included 
in  the  interval  from  53  to  594  feet,  or  less,  from  the  surface.  Orbi- 
tulina  continues  to  the  depth  of  1036  feet.  From  about  1270  to  1770 
the  cuttings  show  numerous  layers  of  blue  clay  and  shale  alternating 
with  limestones  and  marls  together  with  red  calcareous  clays  and 
shales  and  some  quartz  sand  this  part  of  the  section  presumably 
being  within  the  Travis  Peak  formation.  At  1799  feet  and  below  to 
the  bottom  of  the  well,  1905  feet,  the  cuttings  indicate  shists  similar 
to  those  of  the  deep  well  on  the  Leon  Springs  Reservation.  The 
formations  encountered  in  this  well  may  be  tentatively  given  as  fol- 
lows: Buda,  0-14  feet;  Del  Rio,  14-53  feet;  Georgetown,  from 

about  53  to  about  95  feet;  Edwards,  (including  Comanche  Peak 
and  Walnut  clays  if  present)  from  about  95  to  580  feet;  Glenrose 
and  Travis  Peak  (not  inclusive  of  basement  sands)  580  to  about 
1710  feet.  Basement  sands  1710  to  1790  feet.  Below  179*0  feet 
to  the  depth  of  the  well  (1910  feet)  is  pre-Cambrian  schist. 

With  regard  to  schists  Dr.  Udden  states:  The  two  dark  schists  seen 
in  the  lowest  one  hundred  feet  of  this  boring  were  carefully  tested 
by  J.  H.  Stullken  and  found  to  contain  four  per  cent  of  fixed  carbon, 
but  practically  no  combined  carbon.  This  fixed  carbon  is  graphite. 
Tests  for  manganese  were  negative.  The  formation  represented  is 
probably  the  Pack  Saddle  schist. 

This  well  is  of  especial  interest  as  giving  practically  the  full  sec- 
tion of  the  Comanchean,  and  also  as  indicating  the  presence  of 
schists  beneath  the  Comanchean  immediately  south  of  the  Balcones 
Escarpment.  Of  the  Comanchean  formations  there  is  wanting  at 


132 


University  of  Texas  Bulletin 


this  well  only  the  upper  part  of  the  Buda.  The  actual  thick- 
ness of  Comanchean  drilled  through  is  1770  feet.  To  this  should 
be  added  about  50  feet  to  account  for  the  full  thickness  of  the 
Buda  limestone.  Thus  the  Comanchean  at  this  locality  is  about 
1820  feet  thick. 

Log  of  well  at  Camp  Bullis  Reservation,  San  Antonio,  Bexar 
County,  Texas,  August,  1919.  Furnished  by  F.  G.  Chamberlain, 
Constr.  Q-M.,  Camp,  Travis. 

Buff  colored  limestone  0-  7 

Buff  colored  limestone,  lighter  than  above 7-  14 

Buff  colored  marl  14-  38 

Yellow  marl  38-  50 

Yellow  clay  50-  53 

Straw  colored  limestone  53-  65 

Yellow  limestone,  fine  texture  65-  68 

White  limestone  68-  7 2 

Yellow  limestone  72-  78 

White  limestone  78-  89 

Cream  colored  limestone  89-  93 

White  limestone  x 93-  113 

Cream  and  light  gray  limestone  113-  118 

Light  gray  limestone  with  gray  flint 118-  124 

Cream  and  light  gray  limestone 124-  129 

Compact  gray  limestone  129-  14  6 

Cream  colored  limestone,  some  flint  146-  158 

Cream  colored  and  light  gray  limestone 15  8-  170 

Compact  cream  colored  limestone  170-  186 

Cream  and  light  gray  limestone 186-  194 

Cream  colored  and  some  yellow  limestone 194-  197 

Grayish  white  limestone  197-  207* 

Compact  cream  colored  limestone  207-  221 

Light  cream  colored  limestone  221-  230 

Yellow  foraminiferal  limestone 230-  232 

Yellow  limestone  red  blotches  232-  237 

Yellow  and  gray  limestone,  red  streaks 237-  244 

Blue  limestone  244-  246 

Bluish  gray  limestone  246-  255 

Yellow  limestone  255-  260 

Yellow  and  gray  limestone  260-  277 

Yellow  limestone  277-  288 

Yellow  limestone  and  light  gray  sandstone 288-  292 

Light  gray  dolomite  292-  302 

Gray  limestone  302-  315 

Gray  dolomite  315-  325 

Gray  limestone  325-  331 

Dolomitic  gray  limestone  331-  348 


Geology  and  Mineral  Resources  of  Bexar  Comity  133 


Oolitic  foraminiferal  gray  limestone  34  8-  352 

Gray  marly  limestone 3 52-  360 

Gray  impure  limestone  360-  387 

Gray  fine  grained  limestone  . . 387-  392 

Light  blue  gray  limestone  392-  397 

Fine-grained  gray  limestone  397-  415 

Gray  soft  marly  limestone  ...» 415-  456 

Gray  oolitic  foraminiferal  limestone  456-  472 

Gray  marly  limestone . . . . 4 72-  493 

Gray  soft  organic  limestone  493-  515 

Gray  dolomite,  limestone, . some  shale  515-  520 

Gray  foraminiferal  limestone  520-  530 

Gray  dolomite,  limestone,  some  quartz  sand 530-  535 

Gray  organic  fragmental  limestone  535-  608 

White  foraminiferal  limestone  60  8-  612 

White  fine-grained  limestone 612-  617 

White  porous  organic  fragmental  limestone 617-  626 

White  limestone,  some  quartz  sand 62  6-  630 

Light  gray  foraminiferal  and  organic  fragmental 

limestone  636-  641 

Gray  limestone,  some  bluish  gray  marly  shale 641-  64  6 

Gray  limestone  64  6-  655 

Fragment  of  stalactite 65  5-  6 60 

Gray  foraminiferal  and  organic  fragmental  limestone.  . 660-  6 79 

Gray  marly  limestone  and  bluish  gray  marly  shale.  ...  679-  683 

Light  gray  foraminiferal  and  organic  fragmental 

limestone  683-  707 

Bluish  gray  marl  707-  737 

Light  gray  marly  limestone 737-  743 

Light  gray  limestone  74  3-10  90 

Gray  limestone  1090-1100 

Dark  gray  limestone  1100-1112 

Dark  gray  limestone  and  gray  marl  . ; 1112-1119 

Gray  limestone  and  white  marl  1119-1120 

Gray  limestone  and  gray  marl  1120-1125 

Gray  limestone,  organic  fragmental  1125-1144 

Gray  limestone,  some  gray  marl  1144-1150 

Dark  gray  marl  and  .some  dark  gray  limestone 1150-1161 

Gray  marl  1161-1167 

Gray  limestone,  white  limestone,  blue  marl 1167-1173 

White  and  dark  gray  marl,  some  yellow  limestone.  . . .1173-1179 

Light  gray  limestone  1179-1186 

Light  gray  marly  limestone  1186-1209 

Blue  and  white  marly  limestone 1209-1219 

Light  gray  marly  limestone 1219-1232 

Gray  and  cream  colored  limestone  1232-1240 


134  University  of  Texas  Bulletin 

Greenish  gray  marl,  some  fine  gray  sandstone 1240-12  47 

Light  gray  and  marly  limestone 1247-1253. 

Light  blue  marly  clay  1253-1255 

Fragment  of  echinoid  spine,  cytherea 1255-1258 

Gray  limestone  1258-1259 

Light  buff  colored  limestone,  some  marl,  pyrite 

and  sand  1259-1262 

Gray  marl  1262-1269 

Buff  colored  limestone,  gray  limestone,  gray  marl, 

some  calcite,  sandstone,  and  chert 1269-1270 

Blue  and  white  marl  1270-1279 

Light  blue  shale,  some  white  marl 1279-1284 

Blue  marly  clay  1284-1303 

Dark  gray  organic  fragmental  limestone 1303-1310 

Blue  marly  shale,  some  white  marl  and  fine  buff 

colored  limestone  1310-1316 

Blue  marl  with  gray  limestone 1316-1322 

Blue  marly  shale  1322-1334 

Dark  gfay  organic  fragmental  limestone 1334-1345 

Gray  organic  limestone  1345-1475 

Blue  marly  shale,  some  quartz  and  sand 1475-1479 

Blue  marly  shale  and  some  gray  limestone 1479-1484 

Blue  marly  shale  and  some  sand 148  4-1501 

Soft  blue  marl  1501-1528 

Dark  olive  green  and  some  light  gray  marl.  1528-1533 

Bluish  green  marl  and  some  light  gray  marl 1533-1539 

Bluish  gray  marl,  some  marly  shale,  and  quartz 1539-1549 

Blue  marly  shale  1549-1623 

Soft  blue  calcareous  shale 1623-1625 

Light  red  marly  shale  1625-1647 

Soft  light  green  marl  . . . 1647-1654 

Bluish  gray  marl  1654-1657 

Brownish  gray  marl  1657-1660 

Light  gray  marl  1660-16  66 

Light  greenish  gray  marl  1666-1673 

Light  brownish  colored  marl,  much  sand 1673-1675 

Light  brownish  colored  marl  and  less  sand : . . .1675-1689 

Light  colored  marl , 1689-1703 

Light  buff  colored  siliceous  limestone 1703-1711 

Light  buff  colored  calcareous  sand 1711-1766 

Light  buff  colored  limestone  with  fine  and  coarse  sand . 1766-1770 

Dull  yellowish  gray  schistose  shale * 1770-1779 

Yellowish  gray  schist,  part  purple 1799-1802 

Dirty  brownish  gray  and  bluish  gray  schist 180  2-1808 

Dark  and  light  brownish  gray  schist .1808-1816 

Slightly  micaceous  schist,  white  and  gray  quartz 1816-1822 


Geology  and  Mineral  Resources  of  Bexar  County  135 


Dark  gray  schist,  some  quartz 1822-1830 

Dark  gray,  dull  red  and  purplish  schist,  some  quartz.  .1830-1835 

Dark  gray  schist,  some  greenish  and  reddish 1835-1847 

Dark  with- little  pinkish  gray  schist 1847-1850 

Dark  gray  schist  with  reddish  and  light  greenish  gray . 1850-1869 

Very  dark  almost  black  graphitic  schist 1869-1875 

Schist,  dark  gray,  reddish,  and  greenish  gray 1875-1895 

Like  preceding  but  more  green 1895-1900 

Blackish  gray  graphitic  schist,  some  quartz 1900-1910 


WELLS  TERMINATING  IN  THE  COMANCHEAN 

The  term  “non-flowing”  is  used  for  wells  in  which  the  water 
rises  in  the  boring  but  does  not  reach  the  surface.  “Flowing” 
wells  are  those  in  which  the  water  overflows  at  the  surface. 
The  head  of  the  water  above  or  below  the  surface  is  given  for 
some  of  the  wells;  however,  the  head  varies  considerably,  as 
already  stated,  wdth  the  season,  and  the  record  for  any  well  is 
likely  to  vary  according  to  the  season  in  which  the  measure- 
ment was  made.  In  the  well  records,  the  following  data  are 
given  in  order,  so  far  as  available:  Name  of  owner;  location 
of  well ; depth ; elevation  at  the  well ; water,  whether  flowing 
or  non-flowing;  elevation  of  the  top  surface  of  the  Del  Rio< 
formation  above  or  below  sea  level.  These  data  are  followed 
by  the  log  of  the  well  if  available.  The  approximate  location 
of  most  of  the  wells  is  indicated  on  the  contour  map  by  the 
entry  showing  the  level  of  the  top  surface  of  the  Del  Rio 
formation. 

With  the  elevation  of  the  top  of  the  Del  Rio  recorded,  the 
level  of  the  other  Comanchean  and  Cretaceous  formations  can 
be  approximately  determined.  The  top  of  the  Comanchean 
(base  of  the  Upper  Cretaceous)  lies  about  65  or  70  feet  higher 
than  the  Del  Rio;  the  Georgetown-Edwards  series  of  lime- 
stones, the  principal  water  reservoirs  of  this  county,  lie  im- 
mediately below  the  Del  Rio  or  about  70  feet  lower  than  the 
elevation  given.  The  Upper  Cretaceous  formations  are  1200 
or  1300  feet  thick.  An  asterisk  placed  after  the  number  of  the 
well  in  the  table  indicates  that  a log  or  other  data  are  given 
following  the  tabulated  record. 


WELLS  TERMINATING  1JS  TJH£  COMANCHEAN  (.LUVVEK  CKETACEUUS;  FORMATIONS. 


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Hornenberger 9 miles  nortbwestt 570  Non-flowing  400-  470±  470  Austin  to  Comanchean. 


64  | Hubble,  L.  Menchaca  Streetf  490  670 


Geology  and  Mineral  Resources  of  Bexar  Comity 


139 


WELLS  TERMINATING  IN  THE  COMANCHEAN  (LOWER  CRETACEOUS)  FORMATIONS— Continued. 


140 


University  of  Texas  Bulletin 


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124*1  Terrell  Hot  Wells—  5.2  miles  southf. 


WELLS  TERMINATING  IN  THE  COMANCHEAN  (LOWER  CRETACEOUS)  FORMATIONS— Continued. 


142 


University  of  Texas  Bulletin 


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Log  or  other  additional  record  given  helow  under  the  heading  “Supplementary  Data.’ 
(Location  indicated  on  contour  map. 


Geology  and  Mineral  Resources  of  Bexar  County  143 


SUPPLEMENTARY  DATA  ON  WELLS’  TERMINATING  IN  THE 
COMANCHEAN 

The  following  data  including  logs  is  supplementary  to  that 
given  in  the  preceeding  tabulated  records. 

3.  H.  J.  Ackerman,  6 miles  east  of  San  Antonio,  east  side  of  tlie 
W.  W.  White  Road,  % mile  south  of  St.  Hedwig  Road.  This  well 
is  near  the  limits  of  the  area  of  surface  flow  from  the  Georgetown- 
Edwards  limestones.  When  first  drilled,  the  well  is  said  to  have 
flowed  slightly  over  the  pipe  but  to  have  subsequently  ceased  to  flow. 
The  well  is  also  near  the  south  limits  of  non-sulphur  water  in  these 
limestones. 

5.  Alamo  Water  Works,  Alamo  Heights.  Lorenz  Bros.,  drillers. 


Log  by  drillers  from  memory. 

Yellow  clay  (Austin?)  0-  140 

Yellow  rock  (Austin)  140-  350 

(First)  mud  hole  (Eagleford) 350-  380 

.White  rock  (Buda)  380-  430 

Dark  blue  mud,  caves  (Del  Rio) 430-  500 

Yellow  sand  rock  (limestone?)  500-  540 


6.  D.  J.  Allen,  in  Kelly  Field  south  of  Pearsall  (Frio)  Road,  1 
mile  S.  W.  of  city  limits.  T.  H.  Little,  driller,  1910. 


Gravel  and  yellow  clay  (Pleistocene)  0-  60 

Shale  (Taylor  and  Navarro)  60-  600 

White  limestone  (Austin) 600-  900 

Lignite  of  shale  (Eagleford) 900-  940 

Hard  rock  (Buda)  940-1000 

Mud  hole  (Del  Rio)  1000-1054 

Brown  and  white  limestone  v 1054-1254 

White  and  gray  limestones  1254-1595 


The  gravel  deposits  of  this  well  are  those  of  the  Pleistocene. 
Aside  from  these  flood-plain  deposits  the  materials  to  the  depth  of 
600  feet  represent  the  Taylor  and  a part  of  the  Navarro.  The  Austin 
formation  is  recorded  as  “white  limestone,”  600  to  900  feet.  The 
Eagleford,  “lignite”  is  given  as  40  feet;  the  Buda,  “white  rock,” 
60  feet;  and  the  Rel  Rio  “mud  hole”  as  54  feet.  The  top  of  the 
Comanchean  was  reached  at  940  feet.  The  water-bearing  limestones 
were  here  reached  at  1054  feet  and  were  penetrated  to  540  feet, 
thereby  securing  a very  large  flow  of  water,  the  well  being  re- 
ported to  yield  3000  gals,  per  minute  by  pumping.  Mr.  Allen  has 
several  other  similar  wells  on  this  property. 

12.  Ed  E.  Basse,  west  side  S.  A.  & A.  P.  Ry.,  south  side  Olmus 


144 


University  of  Texas  Bulletin 


Creek,  5 miles  north  of  San  Antonio.  Alex  Lorenz,  driller,  l.og 


by  driller  from  memory. 

Surface  materials  0-  30 

Blue  mud,  thickness  not  recorded 30-  425 

Lignite  (Eagleford)  425-  450 

Not  recorded  (Buda)  450-  500 

Clay  (Del  Rio)  500-  555 

Limestone  (Georgetown)  555-  590 


14.  Mrs.  Kate  Benke,  north  side  of  Culebra  Road  near  the  west 
county  line.  A.  E.  Goforth,  driller.  Log  by  driller  from  memoiy. 


Yellow  clay  and  rock  (Taylor)  0-  300 

White  magnesian  limestone  and  blue  medium  hard 

limestone  (Austin)  300-  785 

Lignite  (Eagleford)  785-  820 

Buda  limestone 820-  880 

Clay  (Del  Rio)  880-  940 

Limestone  (Georgetown-Edwards)  940-1000 


Although  located  within  a mile  or  so  of  the  Balcones  Escarpment, 
the  first  300  feet  of  this  well  with  little  doubt  pass  through  the 
Taylor  formation.  This  is  followed  by  485  feet  most  or  all  of  which 
is  to  be  referred  to  the  Austin,  representing  the  thickest  recorded 
section  of  that  formation.  The  Eagleford  is  assigned  the  usual 
thickness  of  35  feet;  the  Buda,  60  feet;  and  the  Del  Rio  60  feet. 
The  top  of  the  Comanchean  formations  lies  at  the  depth  of  820  feet 
from  the  surface.  The  magnitude  of  faulting  in  this  area  is  indi- 
cated by  the  fact  that  within  two  miles  west  from  this  well  the 
Glenrose  formation  is  seen  lying  at  the  surface  at  elevations  of  from 
1200  to  1400  feet  above  sea  level,  while  in  this  well  the  top  of  the 
Glenrose,  probably  lies  300  feet  or  more  below  sea  level. 

16.  H.  T.  Biering,  west  side  Bandera  Road,  15.6  miles  from 
San  Antonio.  Record  from  owner. 

This  well  is  located  in  the  Del  Rio  plain  a mile  or  so  from  the 
Balcones  Escarpment.  The  surface  materials  at  the  well  are  heavy 
stream  washed  gravel,  although  the  Del  Rio  nearby  lies  at  about' 
the  same  level.  The  well  starting  at  the  Del  Rio  level  terminates 
in  the  Edwards  limestone. 

18.  J.  T.  Blank,  south  side  Castroville  Road,  6 miles  west  of 


San  Antonio. 

Surface  materials,  blue  clay  and  rock  0-  928 

Not  recorded  928-1163 

“Mud  hole”  (Del  Rio) 1163-1228 

Limestone  1228-1483 


The  principal  water  supply  is  reported  to  come  from  only  4 feet 


Geology  and  Mineral  Resources  of  Bexar  County  145 

below  the  surface  of  the  Georgetown-Edwards  limestones.  Above 
this  level  are  the  formations  of  the  Upper  Cretaceous,  the  Eagle- 
ford,  Austin,  Taylor,  and  probably  a part  of  the  Navarro.  The  sur- 
face materials  here  are  the  gravel  flood  plain  deposits. 

19.  Blue  wing  Club,  west  side  of  San  Antonio  River,  12  miles 
south  of  San  Antonio.  Drilled  by  cable.  Jacob  Wolf,  driller.  Show- 
ings of  oil  at  900  feet,  and  continuing  more  or  less  to  1200  feet. 

Sand  1-  5 

Clay,  yellow 5-  85 

Sand,  white,  with  water 85-  90 

Rock,  hard,  blue  90-  92 

Clay,  soft,  blue  92-  112 

Rock,  hard,  blue  112-  115 

Clay,  soft,  blue  115-  133 

Rock,  hard,  blue  ' 133-  135 

Clay,  soft,  blue  135-  150 

Rock,  hard,  gray  . 150-  153 

Clay,  soft,  blue  153-  170 

Rock,  hard,  gray  170--  174 

Clay,  soft,  blue  174-  191 

Rock,  hard,  blue 191-  193 

Clay,  soft,  blue 193-  211 

Rock,  hard,  blue  211-  215 

Clay,  soft,  dark  blue  215-  231 

Rock,  hard,  dark  blue  231-  234 

Clay,  soft,  blue  . 234-  250 

Rock,  hard,  gray 250-  252 

Clay,  soft,  blue 252-  270 

Rock,  hard,  gray 270-  273 

Clay,  soft,  dark  blue  273-  289 

Rock,  hard,  blue 289-  293 

Clay,  soft,  blue  293-  311 

Rock,  hard,  blue 311-  313 

Clay,  soft,  blue  313-  320 

Rock,  hard,  blue 320-  322 

Clay,  soft,  blue 322-  334 

Not  recorded  334-  337 

Rock,  hard,  blue  337-  357 

Clay,  soft,  blue  . . 357-  3 60 

Rock,  hard,  blue  . 360-  383 

Clay,  soft,  blue 3 83-  387 

Rock,  hard,  gray 387-  405 

Clay,  soft,  blue  405-  407 

Rock,  hard,  blue 407-  425 

Rock,  hard,  gray  425-  428 


10-Bex. 


146  University  of  Texas  Bulletin 

Clay,  soft,  dark  blue  42 8-  445 

Rock,  hard,  gray  445-  4 47 

Clay,  soft,  light  blue  447-  4 60 

Rock,  hard,  gray  460-  464 

Shale,  soft,  blue  464-  468 

Rock,  hard  gray 468-  470 

Shale,  soft,  dark 470-  472 

Rock,  hard,  white  472-  478 

Shale,  soft,  dark  blue 478-  567 

Rock,  hard,  blue  567-  569 

Shale,  soft,  blue  569-  728 

Shale  and  boulders,  soft,  blue 728-  755 

Shale,  soft  blue 755-  905 

Sand  rock,  soft,  gray 905-  925 

Shale,  soft,  blue  925-  960 

Shale,  soft  and  hard,  blue 960-  996 

Rock,  soft,  blue  996-1006 

Clay,  soft,  blue  1006-1050 

Shale,  hard,  blue 1050-1072 

Shale,  hard,  blue 1072-1092 

Shale,  hard  blue  1092-1106 

Sand  rock,  hard,  blue 1106-1115 

Shale,  hard,  blue  1115-1145 

Rock,  hard,  gray 1145-1149 

Shale,  hard,  blue  1149-1184 

Rock,  hard,  blue 1184-1191 

Shale,  soft,  blue  1191-1212 

Clay,  soft,  light  blue  1212-1300 

Rock,  hard,  blue 1300-1306 

Shale,  soft,  blue  1306-1356 

Shale,  hard,  blue  1356-1387 

Rock,  hard,  gray 1387-1390 

Clay,  soft,  blue  1390-1409 

Rock,  hard,  light  blue 1409-1446 

Gumbo,  hard,  dark 1446-1746 

Rock,  soft,  white  1746-1850 

Rock,  soft,  blue  1850-1910 

Rock,  hard,  white 1910-1987 

Rock,  hard,  blue 1987-2015 

Rock,  hard,  gray  2015-2054 

Rock,  hard,  light  blue 2054-2080 

Rock,  hard,  gray  2080-2140 

Rock,  soft,  dark  blue 2140-2152 

Rock,  hard,  white  2152-2189 

Rock,  hard  and  soft,  yellow;  water 2189-2269 

Rock,  hard,  white;  no  water • 2269-2304 


Geology  and  Mineral  Resources  of  Befrar  County  147 


Rock,  soft,  yellow;  water  2304-2374 

Rock,  soft,  yellow,  and  hard;  water 2374-2433 

Rock,  hard,  flint;  no  water 2433-2  437 

Rock,  hard,  dark  blue;  no  water  2437-2444 


The  log  of  this  well  is  difficult  to  interpret.  The  driller  states 
that  he  was  unable  to  recognize  either  the  Eagleford  “lignite”  or 
the  Del  Rio  “mud  hole.”  The  water  obtained  from  the  well  is  re- 
ported to  have  had  a temperature  of  117°  and  to  have  had  a head 
of  about  75  feet  above  the  surface.  The  water  which  was  first  ob- 
tained at  the  depth  of  2189  feet,  or  at  the  actual  level  of  about  1700 
feet  below  sea,  is  derived  with  little  doubt  from  the  Georgetown- 
Edwards  limestones.  The  Del  Rio  formation  is  placed  provisionally 
in  this  well  at  2140  feet  from  the  surface  or  at  the  actual  level  of 
about  1685  feet  below  sea.  This  interpretation  is  permissible  from 
the  log. 

21.  D.  Boerman,  south  side  of  Bandera  Road,  11  miles  north- 


west of  San  Antonio.  Record  from  owner. 

Chiefly  limestone  and  shale  (Austin-Eagleford) 0-  280 

Hard  limestone  (Buda)  280-  320 

Mud  hole  (Del  Rio)  320-  385 

Limestones  (Georgetown)  385-  403 


24.  H.  Brendle,  527  Bandera  St.,  about  one  mile  north  of  west 
of  San  Pedro  Springs,  San  Antonio.  Log  published  in  18th  Ann. 
Rpt.,  U.  S.  G.  S.,  p.  293. 

Blue  marl  and  clay  described  as  sea  mud  in  this  well  from  493- 
583  feet,  is  interpreted  as  the  Del  Rio  formation,  which  accordingly 
lies  at  the  level  of  from  227  to  317  feet  above  sea. 

27.  ^ C.  C.  Clamp,  south  of  the  Castroville  Road,  east  of  Leon 
Creek,  6 miles  west  of  San  Antonio.  Log  by  Mr.  Fred  Lewis. 


Clays,  mostly  blue  in  color  (Navarro-Taylor) 0-  662 

White  shale  (Austin?)  662-  825 

White  lime  rock  (Austin)  825-1023 

Lignite  (Eagleford)  1023-1054 

White  limestone  (Buda)  1054-1110 

Mud  hole  (Del  Rio)  1110-1162 

Limestone  1162-1195 

Water  sand  1195-1196 

Limestone  1196-1220 

Crevice,  water  1220-1221 

Sandy  limestone  rock  ...  * 1221-1275 

Crevice,  water  1275-1277 

Limestone  1277-1292 

“Sand”  1292-1308 


148 


University  of  Texas  Bulletin 


Not  recorded  1308-1395 

Limestone  rock  1395-1452 

Aside  from  the  surface  materials  the  first  662  feet  in  this  well 
probably  represent  the  Taylor  and  a part  of  the  Navario  forma- 
tions. The  361  feet  recorded  as  white  shale  and  white  lime  rock 
probably  represent  the  Austin  formation.  The  Eagleford  lignite 
is  assigned  a thickness  of  31  feet;  the  Buda,  56  feet;  and  the  Del 
Rio,  52  feet.  The  water-bearing  limestones  lie  at  the  depth  of  1162 
feet.  As  hearing  on  structural  conditions  it  is  of  interest  to  note 
that  the  Comanchean  formations  here  lie  at  a lower  level  than  at 
the  Allen  well  in  Kelly  Field,  about  2 Y2  miles  farther  south,  the 
Allen  well  being  nearer  the  axis  of  the  San  Antonio  structure,  al- 
ready described. 

28.  Collins  Manufacturing  Company,  900  yds.  northeast  by  north 
of  Courthouse,  San  Antonio.  Record  from  U.  S.  G.  S.  18th  Ann. 
Rpt.,  p.  293.  At  this  well  blue  clays  were  passed  through  from 
about  720  to  800  feet  which  with  little  doubt  represent  the  Del  Rio 
formation.  The  Del  Rio  here  lies  at  about  60  feet  below  sea  level. 

30.  Collins  Gardens,  near  I.  & G.  N.  Ry.  track  below  Union 


Stockyards,  used  for  irrigation.  Jacob  Wolf,  driller. 

Yellow  clay  and  gravel  (Pleistocene)  0-  40 

Blue  clay,  mostly  soft  and  caving  (Navarro-Taylor)  . . .40-  525 

Limestone  (Austin)  ,, 5 25-  855 

Lignite  (Eagleford)  855-  890 

Hard  limestone  (Buda)  890-  930 

Mud  hole  (Del  Rio)  930-1000 

Limestone  


The  blue  clays  of  this  well  from  40  to  525  feet  represent  the 
Taylor  and  probably  a part  of  the  Navarro  formations.  The  lime- 
stones which  may  be  assigned  to  the  Austin  formation  have  a thick- 
ness of  330  feet.  The  Buda  limestone,  the  first  of  the  Coman- 
chean formations,  is  reported  at  890  feet.  In  this  well  good  water 
is  reported  to  have  been  obtained  while  in  the  limestones  of  the 
Austin  formation,  at  the  depth  of  638  feet. 

33.  Dickenson  well,  north  side  of  Culebra  Road,  8 miles  north- 
west of  San  Antonio.  Alex  Lorenz,  driller.  Elevation  of  Del  Rio, 
353  feet. 

Surface  materials,  blue  clay  and  limestone  (Taylor- 


Austin)  0-  420 

Lignite  (Eagleford)  420-  447 

Hard  rock  (Buda)  447-  497 

Mud  hole  (Del  Rio)  497-567 

Limestone  rock  (Georgetown-Ed wards)  567-  602 


Geology  and  Mineral  Resources  of  Bexar  County  149 


The  surface  materials  at  this  well  include  remnants  of  the  grav- 
els of  the  Uvalde  formation.  A part  of  the  clays  represent  the 
lower  part  of  the  Taylor  formation  as  indicated  by  exposures  nearby. 
The  limestones  under  the  clays  to  the  depth  of  420  feet  are  of  the 
Austin  formation.  The  Comanchean  is  entered  at  447  feet  and  the 
water-bearing  Comanchean  limestones  are  reached  at  567  feet. 

42.  Geunther  Milling  Company,  902  Morales  St.,  east  side  of 


I.  & G.  N.  Ry.,  San  Antonio. 

Yellow  clay  and  gravel  (Pleistocene)  0-  50 

Blue  clay  (Taylor)  50-  250 

Soft  gray  rock  (Austin)  250-  350 

White  limestone,  water  (Austin)  350-  550 

Bluish  black  shale,  lignite  (Eagleford) 550-  600 

Hard  white  limestone  (Buda)  600-  650 

Sea  mud  (Del  Rio)  650-  700 

Blue  limestone  700-  750 

“Sand”  and  black  flint  strata,  water 750-  800 

Hard  sandstone  800-  850 

Flint,  gray  (and  limestone)  850-  875 


The  log  of  this  well  as  preserved  is  evidently  a somewhat  gen- 
eralized record.  However,  it  serves  to  place  approximately  the  top 
surface  of  the  water-bearing  limestones  at  700  feet.  Some  part  of 
the  Taylor  formation  here  lies  above  the  Austin  and  Eagleford, 
although  concealed  at  the  surface  by  flood-plain  deposits. 

^ 43.  A.  E.  Goforth,  north  side  Culebra  Road,  18  miles  northwest 
of  San  Antonio.  Goforth,  driller. 

Surface  materials  and  limestone  rock,  the  lower  part 


hard  and  blue  in  color  (Austin  formation) 0-  349 

Lignite  (Eagleford)* 34  9-  384 

Hard  limestone  (Buda)  384-  444 

Del  Rio  clay  (mud)  444-  504 

Limestone  rock  (Georgetown-Edwards)  504-  564 

44.  Government  well,  at  Aviation  Post,  on  Austin  Road,  about 
6 miles  from  San  Antonio,  Benkendorfer,  driller. 

Soil  0^  2 

Yellow  clay  2-  55 

Blue  clay  (small  vein  good  water  at  190,  rose  within 

100  ft.  of  surface)  55-  190 

Magnesian  limestone,  soft,  light  blue  190-210 

Soft  shale  210-  220 

Light  gray  hard  limestones 220-  240 

Blue  gray  very  hard  limestone 24  0-  2 60 

Hard  white  limestone  260-  280 


150  University  of  Texas  Bulletin 

Soft  white  limestone 280-  300 

Blue  and  white  hard  limestone 300-  320 

Not  recorded  320-  330 

Hard  white  and  blue  limestones  330-  340 

(8"  casing  rested  at  340  ft) 

Very  hard  white  limestone  340-  353 

Lignite,  black  and  soft  (Eagleford)  . . 353-  380 

Gray  shaly  rock  380-  400 

White  hard  limestone  400-  418 

Del  Rio  “mud,”  soft,  blue-gray 418-  494 

(6"  casing  rested  at  494  ft) 

Limestone,  slightly  yellow,  hard  494-  557 

Limestone,  light  in  color  . . . 557-  575 

Porous  limestone  575-  580 

Hard  brown  limestone  580-  590 

Soft  limestone  590-  625 

Hard  brown  limestones 625-  655 

Flinty  limestone  655-  657 

Soft  limestone  657-  671 

White  hard  limestone  671-  680 

Soft  brown  limestone  680-  690 

Hard  limestone  690-  748 

Black  flint  748-  750 

Hard  yellow  limestone 750-  795 

Very  hard  limestone 795-  835 

Light  brown  soft  sandstone 835-  855 

Light  brown  limestone 855-  874 


The  formation  penetrated  in  this  well  to  the  depth  of  353  feet  is 
chiefly  the  Austin  including  possibly  some  of  the  Taylor  at  the 
surface.  The  combined  thickness  of  the  Eagleford  “lignite”  and 
Buda  “shaly  rock  and  white  limestone”  is  recorded  as  65  feet.  This 
is  unusually  thin  for  these  formations  unless  a part  of  the  Eagle- 
ford has  been  included  with  the  limestones  referred  to  the  Austin. 
All  wells  bejtween  the  east  city  limits  of  San  Antonio  and  Salado 
Creek  record  a reduced  thickness  of  the  Eagleford,  Buda,  and  Del 
Rio  formations. 

45.  Government  well,  Fort  Sam  Houston,  near  west  limits  of 
Government  Reservation  between  Pine  Street  and  River  Avenue, 
San  Antonio.  Judson,  driller;  1903;  depth  729  ft.;  casing  10-in. 
to  630  ft.  Elevation,  689.  Non-flowing,  although  stood  in  well 
when  completed  within  a few  feet  of  the  surface.  Elevation  Del 


Rio,  69. 

Blue  loam  and  flint  boulders 0-  3 

Yellow  clay  3-  41 

Blue  clay  41-  258 


Magnesian  limestone.  Small  streak  of  good  water  at 


Geology  and  Mineral  Resources  of  Bexar  County  151 


350  ft 258-  354 

Gray  limestone,  sulphur  water 354-  392 

Gray  limestone,  hard  392-  429 

Yellow  limestone  429-  468 

Gray  limestone  4 68-  535 

“Lignite”  (Del  Rio)  535-  566 

Gray  limestone  (Buda) 566-  620 

Blue  clay  with  shells  (Del  Rio).. 620-  673 

Blue  limestone  673-  688 

Hard  yellow  limestone 688-  706 

Calcareous  limestone  706-  708 

Struck  water  at  705  ft. 

Open  cavity  708-  713 

Hard  limestone  with  fissures  filled  with  clay 713-729 


This  well  may  be  compared  with  the  new  city  well  drilled  at  the 
north  city  limits  in  1918.  Although  only  about  1 mile  farther 
north,  the  Del  Rio  at  the  city  well  is  found  at  the  level  497,  or  . 
more  than  400  feet  higher  than  in  this  well,  the  two  wells  being 
separated  by  a large  fault. 

46.  F.  Grote,  south  side  of  Bulverde  Road,  OV2  miles  from  San 


Antonio.  Alex  Lorenz,  driller. 

Soft  “adobe”  lime 0-  17 

Hard  limestone  (Austin)  17-  187 

Lignite  (Eagleford)  187-  222 

Hard  limestone  (Buda)  222-  272 

Clay  (Del  Rio)  272-  332 

Hard  limestones  (Georgetown)  332-  339 


This  well  starts  in  the  Austin  formation  surface  exposures  of 
which  are  seen  nearby.  The  Comanchean  formations  are  entered 
at  the  depth  of  222  feet.  The  water-bearing  limestones  were 
reached  at  332  feet  and  were  drilled  into  only  7 feet.  The  well 
is  located  on  the  structurally  high  area  elsewhere  described  as  the 
San  Antonio  structure. 

49.  Jud  Harrison,  west  side  Blanco  Road  south  of  Coker  cross 
road,  8 V2  miles  north  San  Antonio.  Alex  Lorenz,  driller. 

Not  recorded  (Austin)  0-  185 

Lignite  (Eagleford)  185-  190 

Hard  limestone  (Buda)  190-  245 

Clay  (Del  Rio)  245-  300 

Limestone  (Georgetown)  300-  328 

56.  Herff  well,  formerly  the  Werner  property,  north  of  Castro- 
ville  Road,  between  Stephenson  Road  and  West  34th  St.  Benken- 
dorfer,  driller.  Record  from  driller’s  notebook.  Del  Rio  mud 


152 


University  of  Texas  Bulletin 


recorded  at  from  1000  to  1060  feet,  the  water-bearing  Coman- 
chean  limestones  thus  lying  at  the  level  350  below  sea. 


Surface  clay  and  gravel  (Pleistocene)  0-  31 

Yellow  clay  (Navarro)  31-  81 

Blue  clay  (Navarro-Taylor)  81-  621 

Magnesian  limestone  (Austin)  621-  781 

Blue  limestone  (Austin)  781-  811 

White  limestone  (Austin)  811-  951 

Lignite  (Eagleford)  951-  969 

Gray  limestone  (Buda)  969-1050 

Clay  (Del  Rio)  . 1050-1110 

Brown  limestone  1110-1140 

Porous  limestone,  water  rock  1140-1286 


The  surface  clay  and  gravel  at  this  locality  includes  that  of  the 
flood-plain  deposits.  Aside  from  these  surface  materials  the  Upper 
Cretaceous  is  here  recorded  as  having  a thickness  of  over  900  feet, 
•the  Comanchean  limestones  (Buda  formation)  having  been  reached 
at  969  feet.  Judging  from  the  thickness  of  the  Upper  Cretaceous 
there  are  probably  present  here  the  Eagleford,  Austin,  Taylor,  and 
lower  part  of  the  Navarro  formations. 

57.  Hill  and  Roby,  east  side  Pleasanton  Road,  7 XA  miles  south  of 
San  Antonio.  Jacob  Wolff,  driller.  1910.  Depth,  1890.  Elevation 
about  625.  Flowing  warm  sulphur  water. 

In  this  well  the  Del  Rio  clay  is  said  to  have  been  passed  through 
at  from  1695  to  1750  feet,  or  at  the  actual  level  of  from  1060  to 
1125  below  sea.  The  formation  thus  lies  more  than  300  feet  lower 
than  its  estimated  level  in  the  Alta  Vista  oil  field,  a few  miles 
farther  southwest,  and  but  little  less  than  200  feet  lower  than  in 
the  Ripps  well  a short  distance  southeast. 

59.  R.  H.  Hofheintz  on  Pearsall  (Frio)  Road  between  public 
road  and  railway,  just  north  of  Kelly  Field,  four  miles  from  San 
Antonio.  Benkendorfer,  driller. 

In  this  well  the  Comanchean  formations  were  entered  at  950 
feet.  The  overlying  Cretaceous  includes  probably  the  Eagleford, 
Austin,  Taylor  and  the  lower  part  of  the  Navarro  formations,  as 
well  as  the  surface  flood-plain  deposits.  The  Del  Rio  formation  was 
entered  at  1000  feet,  or  at  the  level  of  315  feet  below  sea.  The 
water-bearing  Comanchean  limestones  lie  at  the  depth  of  1054  feet 
and  were  drilled  into  to- the  total  depth  of  1453  feet.  A log?  of  this 
well  is  given  in  Bull.  298,  U.  S.  G.  S.,  p.  268. 

60.  Holtz  well,  on  left  bank  of  Leon  Creek  below  the  Somerset 
Road  crossing,  nine  miles  southwest  of  San  Antonio.  This  well  was 
drilled  by  rotary  by  Holtz  to  a depth  of  1200  feet  where  hard  rock 


Geology  and  Mineral  Resources  of  Bexar  County  153 


was  readied  and  where  the  6"  casing  was  rested.  From  this  depth 
the  well  was  drilled  with  cable  tools  by  Benkendorfer.  Temperature 
of  water  said  to  be  106.5  F. 

7 63.  Hot  Wells  Hotel,  on  San  Juan  Boulevard,  1*4  miles  south  of 
the  south  city  limits  of  San  Antonio,  east  side  of  San  Antonio  river. 
Robert  Newton,  driller. 

Soil  0-  5 

Yellow  clay  5-  15 

Black  sand  15-  20 

Sand  and  gravel,  water 20-  30 

Yellow  clay  30-  52 

Blue  shale  52-  90 

Streaks  of  lignite  90-  95 

Gumbo  and  blue  clay 95-  125 

Sandy  shale  125-  175 

Gumbo  175-  323 

Sand  rock  323-  325 

Gumbo  325-  337 

Sand  rock  337-  340 

Gumbo  340-  351 

Rock 351-  353 

Sandy  shale m . 353-  412 

Gumbo  412-  506 

Sandy  shale 506-  577 

Sand  rock,  oil  show  577-  587 

Gumbo  587-  597 

Sandy  shale  597-  710 

Hard  gumbo  710-  990 

Lime  rock,  casing  8"  set 990-1003 

Lime  rock  1003-1445? 

Gumbo  and  hard  shale 1445-1454 

Lime  rock  1454-1740 

Hard  shale  1740-1748 

Hard  lime  rock,  pink 1748-1865 

Sand  lime,  some  water 1865-1875 

Porous  rock,  sulphur  water 1875-1878 

This  well  having  been  drilled  by  rotary  does  not  afford  as  defi- 
nite information  as  the  wells  drilled  by  cable  tools.  The  log  is 
given  as  made  out  by  the  driller.  While  the  interpretation  of  the 
log  is  in  doubt,  it  is  probable  that  aside  from  surface  materials, 
the  first  990  feet  represents  chiefly  Navarro  and  Taylor  formations; 
while  from  990  to  about  1445  represents  the  limestones  of  the 
Austin,  Eagleford,  and  Buda  formations.  On  this  interpretation 
the  Del  Rio  lies  here  at  about  1445  feet  from  the  surface  or  about 
870  feet  below  sea  level. 


154 


University  of  Texas  Bulletin 


>/  67.  Kearney  Oil  and  Pipe  Line  Company,  No.  3,  west  side  of 

Palo  Alto  Road  about  one  mile  south  of  Leon  Creek  crossing. 

Yellow  clay  0-  42 

Blue  clay  42-  125 

Black  sand,  gas  show 125-  161 

Blue  clay 161-  226 

Sand  rock  226-  234 

Gumbo  234-  261 

Sand  rock  261-  262 

Gumbo  262-  268 

Soft  rock  268-  269 

Gumbo  269-  273 

Soft  rock  273-  275 

Gumbo  and  soft  rock 275-  392 

Shale  392-  433 

Hard  rock  433-  449 

Gumbo  449-  486 

Gumbo  and  shale,  oil  show 486-  527 

Gumbo  527-  569 

Gumbo  and  shale,  oil  show 569-  621 

Soft  rock,  oil  show  621-  636 

Gumbo  636-  703 

Shale  703-  724 

Gumbo  724-  745 

Not  recorded  745-  837 

Rock  (limestone)  837-  869 

Gumbo  869-  872 

Soft  rock  872-  886 

Gumbo  886<-  890 

Soft  rock  890-  892 

Gumbo  892-  957 

Hard  rock  (limestone)  957-1063 

Yellow  rock  (limestone)  1063-1151 

Sand,  heavy  oil,  about  2 bbls.  per  day 1151-1161 

White  limestone  and  water 1161-1211 

Yellow  limestone  and  water  (sulphur) 1211-1221 

White  limestone  1221-1321 

Lignite,  kind  of  mud  (Eagleford) 1321-1357 

Black  limestone  (Buda) 1357-1451 

Mud  hole,  sea  shells  (Del  Rio)  1451-1491 

Hard  black  limestone 1491-1591 

Warm  sulphur  water 1591-1861 

White  rock,  salty  water 1861-1881 

Cold  water,  brackish 1881-1991 

Not  recorded  1991-2355 

This  well,  log  of  which  has  been  given  by  Mr.  Kearney,  affords 
a very  important  and  reliable  record  of  the  depth  of  the  formations 


Geology  and  Mineral  Resources  of  Bexar  County  155 

at  this  locality.  The  well  is  located  within  the  belt  of  Tertiary 
exposures,  provisionally  mapped  as  Midway.  The  interval  from  the 
surface  to  957  is  assigned  to  the  Midway,  Navarro  and  Taylor  for- 
mations. The  Austin  formation  apparently  is  represented  by  the 
interval  from  957  to  1321  feet,  364  feet,  consisting  chiefly  of  lime- 
stones, with  some  slight  production  of  heavy  oil  at  1151  feet.  The 
record  of  the  Eagleford  “lignite”,  Buda  limestone,  and  Del  Rio 
clay  is  unmistakable.  To  the  Eagleford  is  assigned  a thickness 
of  36  feet,  to  the  Buda,  94  feet;  and  to  the  Del  Rio,  40  feet.  The 
Georgetown-Edwards  limestones  were  entered  at  1491  feet.  Warm 
sulphur  water  was  obtained  in  these  limestones.  The  drill  hole 
was  continued  below  the  top  of  these  limesones  964  feet,  probably 
terminating  in  the  Glenrose  formation.  Mr.  Kearney  believes  that 
the  water  obtained  below  1881  feet  was  neither  so  warm  nor 
so  salty  as  that  from  a somewhat  higher  level.  Mr.  Jacob  Wolff 
believes  that  the  cool  non-sulphur  water  lies  below  1900  feet  from 
the  surface.  The  interval  between  the  oil  sands  in  the  Austin  and 
the  top  of  the  Del  Rio  formation  in  this  well  is  about  300  feet. 
The  whole  thickness  of  the  upper  .Cretaceous  as  indicaed  by  this  well 
is  about,  or  a little  more  than,  1200  feet.  The  stratigraphic  in- 
terval from  the  greensand  horizon  near  the  top  of  the  Navarro 
to  the  top  of  the  Del  Rio  is  1326  feet.  The  actual  level  of  the  Del 
Rio  at  this  locality  is  841  feet  below  sea  level. 

73.  Well  in  Lakeview  Addition,  near  24th  Street,  west  part  of 


San  Antonio,  north  of  Elmendorf  Lake. 

Black  soil  . . . 0-  4 

Yellow  clay  4-  31 

Soft  blue  clay 31-  43 

Not  recorded  43-  187 

Hard  streaks  at 187 

Not  recorded 187-  190 

Sand  rock,  six  inches  at 190 

Not  recorded  1 190-  206 

Hard  lime  rock.... 206-  281 

Black  lignite  (Eagleford) 283-  291 

Streaks  black  lignite  at 349 

Not  fully  recorded • 291-  441 

Blue  mud  (Del  Rio) 441-  494 

Soft  dark  sandrock 494-  522 

“Granite” 522-  586 

Sand  rock  with  water 586-  591 


This  log  is  very  unusual  and  is  difficult  to  interpret.  If  the  blue 
clay  at  441  feet  represents  the  Del  Rio,  the  formation  lies  here  at 
about  the  actual  level  of  239  feet  above  the  sea. 


156 


University  of  Texas  Bulletin 


74.  W.  F.  Legler,  on  north  side  Castroville  Road,  5 miles  west 


of  San  Antonio.  Alex  Lorenz,  driller. 

Soil  0-  5 

Clay  and  gravel  (Pleistocene) 5-  18 

Yellow  clay  (Navarro) 18-  52 

Blue  clay  (Navarro-Taylor) 52-  670 

White  shale  (Austin) 670-  910 

Limestone  (Austin)  910-1080 

Lignite  (Eagleford)  1080-1108 

Hard  rock  (Buda)  1108-1167 

Clay  (Del  Rio) 1167-1220 

Limestones,  water  bearing  at  successive  horizons 1220-1555 


The  top  of  the  Comanchean  formation  in  this  well  is  reached 
at  1108  feet  below  the  surface,  the  upper  Cretaceous  formations 
present  being  probaly  the  Eagleford,  28  feet;  Austin,  310  feet; 
Taylor  and  loweri  part  of  the  Navarro,  618  feet;  and  the  Pleistocene 
flood-plain  deposits  amounting  to  about  18  feet. 


75.  J.  Locke,  west  side  of  Blanco  Road,  5 miles  north  of  San 
Antonio.  Alex  Lorenz,  driller. 

Yellow  calcareous  marl  (Austin) 0-  50 

Blue  limestone  rock  (Austin) 50-  250 

Lignite  (Eagleford)  250-  265 

Hard  white  rock  (Buda) 265-  310 

Sea  mud  (Del  Rio) 310-  370 

Limestone  (Georgetown)  370-  385 

77.  Alex  Lorenz,  north  side  Bulverde  Road,  about  6 miles  north 
of  San  Antonio. 

“Adobe”  0-  25 

Blue  “mud”  rock  (Austin)  25-  150 

White  limestone  rock  (Austin)  150-  270 

Lignite  (Eagleford)  270-  295 

Hard  limestone  (Buda)  295-  345 

Clay  (Del  Rio)  345-  400 

Limestone  rock  (Georgetown)  400-  420 


80.  B.  F.  Masterson,  about  1 mile  north  of  the  Castroville  Road, 
18  miles  west  of  San  Antonio.  Test  well  for  oil.  Record  from 
Geo.  B.  Mechem  Co. 

In  this  well,  according  to  a summary  of  the  log  supplied  by  the 
owners,  the  Del  Rio  formation  is  believed  to  have  been  entered  at 
the  depth  of  734  feet  from  the  surface,  and  to  be  83  feet  thick. 
The  Georgetown-Edwards  limestones  were  reached  at  817  feet,  and 
the  drill  hole  was  continued  to  1620  feet  probably  terminating  in 
the  Glenrose  formation. 


Geology  and  Mineral  Resources  of  Bexar  Comity 


57 


81.  Chas.  Matyear,  near  24th  Street,  in  Lakeview  Addition,  San 
Antonio.  Alex.  Lorenz,  driller.  Elevation,  678.  Elevation  of 


Del  Rio,  186. 

Black  earth  0-  4 

Yellow  clay  4-  31 

Soft  blue  clay  31-  43 

Not  recorded  43-  187 

Hard  streaks  187 

Black  sand  rock  190 

Hard  lime  rock  206-  281 

Like  black  lignite  (Eagleford) . . . . 283-  291 

Streak  black  lignite.... 349 

Blue  mud  (Del  Rio) ! 441-  494 

Soft  dark  sandrock 519-  522 

“Granite”  . . 584-  586 

Sand  rock,  water 591 


82.  Medina  Fuller’s  Earth  Company,  about  one  mile  north  of 
Castroville  Road,  and  west  of  Cagnon  Cross  Road,  16  miles  west  of 
San  Antonio.  Alex.  Lorenz,  driller.  From  the  stratigraphic  inter- 
val from  the  surface  to  the  Del  Rio  formation  it  appears  that  this 
well  starts  in  the  Taylor  formation. 


Blue  marl  0-  400 

White  soft  rock  400-  600 

Eagleford  600-  635 

Buda  635-  685 

Del  Rio  685-  750 

Georgetown  750-  778 

Actual  level,  Del  Rio 100 -t- 


* 83.  Medina  Oil  Company,  south  of  Leon  Creek,  west  of  Apple- 
white  Road.  Jacob  Wolff,  driller.  4-inch  casing  set  at  1530  feet; 
first  flow  of  sulphur  water  at  1540  feet;  second  flow,  1800  feet; 


depth  of  well  1833  feet. 

Yellow  clay  1_  15 

Gravel  15_  25 

Black  sand  25-  50 

Blue  clay  50-  100 

Blue  rock  100-  104 

Blue  clay  104-  124 

Blue  rock,  showing  oil  . 124-  129 

Blue  clay  129-  145 

Blue  rock  145-  153 

Light  blue  clay 153-  165 

Blue  rock  165-  169 

Blue  clay  . 16  9-  176 

Blue  rock  176-  186 


158  University  of  Texas  Bulletin 

Blue  clay  186-  200 

Blue  rock 200-  206 

Blue  clay  206-  217 

Gray  rock  217-  255 

Clay  and  sand,  gas 255-  296 

Gray  rock  296-  302 

Blue  clay  302-  348 

Gray  rock  348-  355 

Light  blue  clay 355-  408 

Blue  rock  408-  416 

Blue  gumbo  416-  436 

Dark  blue  clay  436-  496 

Dark  gray  rock 496-  500 

Hard  blue  clay  500-  548 

Dark  gray  rock . 548-  552 

Dark  gray  shale,  gas  and  oil 552-  564 

Dark  gray  rock 564-  567 

Dark  clay  and  sand,  gas  and  oil 567-  630 

Gray  rock  630-  633 

Dark  hard  clay 633-  665 

Hard  gray  rock 665-  671 

Hard  blue  clay  671-  728 

Gray  rock  728-  736 

Blue  clay  736-  783 

Black  rock 783-  791 

Dark  clay  791-  806 

Dark  rock  806-  836 

Gray  shale  with  oil 836-  858 

Hard  dark  rock  858-  912 

Hard  light  blue  rock  912-  922 

Hard  dark  gray  rock  922-  943 

Hard  white  rock 943-  950 

Hard  light  blue  rock 950-  953 

Yellow  shale  with  oil 953-  957 

White  rock  957-  960 

. Light  blue  rock 960-  964 

Yellow  shale  with  oil 964-  982 

Light  blue  rock  982-  986 

White  soft  rock  986-  990 

Light  blue  hard  rock 990-  994 

Yellow  shale  with  oil 994-1012 

White  rock  1012-1014 

Blue  rock  1014-1015 

In  this  well,  the  Del  Rio  formation  is  reported  at  1450  feet  from 
the  surface,  or  at  about  920  feet  below  sea  level.  At  25  feet  there 
is  reported  a black  sand  which  very  possibly  is  the  glauconitic 


Geology  and  Mineral  Resources  of  Bexar  County  159 

sand  horizon  of  the  Navarro  formation.  If  so,  the  thickness  of  the 
Upper  Cretaceous  as  recorded  in  this  well  is  142  5 feet,  which  is 
somewhat  greater  than  farther  northwest  as  indicated  by  the  Kear- 
ney, Vogt,  and  Ridder  wells. 

93.  A.  J.  Ridder,  east  side  of  Medina  River,  13  miles  southwest 
of  San  Antonio,  north  of  Pearsall  Road.  Several  wells  on  this 
property.  L.  N.  Knight,  driller.  In  all  of  these  wells  the  glau- 
conitic greensand  is  noted,  and  the  wells  are  of  interest  as  indi- 
cating a south  or  southeast  dip.  They  are  as  follows: 

Deep  well,  north  side  Southern  Pacific  track;  depth,  2911  feet; 
elevation  628;  flowing  artesian  water. 

In  this  well  no  water  was  found  until  below  1502  feet,  the  forma- 
tions being  entirely  dry  to  that  depth.  Successive  water  horizons 
between  1557  and  1980  feet  were  found.  A glauconitic  greensand 
horizon  was  recognized  at  165  feet  from  the  surface,  the  greensand 
being  50  or  60  feet  thick.  The  Del  Rio  formation  was  recognized 
at  1444  feet  and  continued  to  1497  feet.  The  limestones  below  the 
Del  Rio  were  drilled  into  1413  feet.  From  this  record  it  appears 
probable  that  the  well  terminated  either  near  the  base  of  the  Glen- 
rose  or  in  the  Travis  Peak  formation.  In  this  connection  it  is  of 
interest  to  note  that  the  driller  reports  having  drilled  into  fossil 
wood  not  petrified,  but  more  or  less  lignitized,  near  the  bottom  of 
this  well. 

This  deep  well  affords  a record  of  practically  the  full  thickness 
of  the  Upper  Cretaceous.  While  the  Buda  is  not  recorded,  its  uni- 
form thickness  of  65  or  70  feet  overlying  the  Del  Rio  makes  it  pos- 
sible to  place  the  top  of  the  Comanchean  at  about  1374  feet  from 
the  surface.  The  greensands  reached  at  165  feet  are  with  little 
doubt  those  of  the  Navarro  formation  as  exposed  on  Leon  Creek. 

The  Upper  Cretaceous  is  therefore  1200  feet  thick  at  this  well, 
possibly  a little  more.  This  agrees  closely  with  the  thickness  of 
these  formations  as  determined  from  the  Kearney  well,  about  6 
miles  farther  southeast,  where  the  Upper  Cretaceous  formations 
appear  to  have  a thickness  of  about  1232  feet. 

Another  measurement  obtained  from  this  well  and  from  the  Kear- 
ney well,  used  in  estimating  the  place  of  the  Del  Rio  in  some  wells, 
is  the  stratigraphic  interval  between  the  glauconitic  greensand  and 
the  top  of  the  Del  Rio  formation.  In  this  well  this  interval  is 
1279  feet;  in  the  Kearney  well,  the  same  interval  was  found  to  be 
1326  feet,  or  47  feet  greater. 

Ridder  well,  near  west  line  of  property.  Elevation  617.  Green- 
sand at  200  feet  from  surface,  or  at  level  of  417  feet  above  sea. 

Ridder  well,  on  north  side  of  Pearsall  Road,  about  % mile  from 
Medina  River.  Elevation  617.  Greensand  at  235  feet  from  the  sur- 
face, or  at  level  382  feet  above  sea. 

Ridder  well,  on  east  side  of  Medina  River.  Elevation  595.  Some 


160 


University  of  Texas  Bulletin 


water  obtained  at  1056  feet;  additional  water  at  1410  feet.  Green- 
sand at  285  feet  from  the  surface,  or  at  level  310  feet  above  sea. 

The  dip  in  the  formations  from  the  deep  well  north  of  the  railway 
to  this  well  on  the  river,  a distance  of  about  one  mile,  according 
to  these  records  is  150  feet.  That  this  dip  continues  to  the  south 
is  indicated  b,y  the  Vogt  well,  subsequently  recorded. 


97.  St.  Louis  College,  between  Culebra  and  Bandera  roads, 
about  5.4  miles  west  of  San  Antonio.  Elevation,  760. 


Flint 

Adobe  

Yellow  clay  

Blue  clay 

Magnesian  lime  rock 

Hard  blue  lime 

Hard  yellow  rock  . . . 

Hard  gray  rock 

Lignite  (Eagleford)  . 
Limestone  (Buda) . . . 
Blue  clay  (Del  Rio) . 
Dark  blue  limestone  . 
Yellow  limestone  . . . 
Crystallized  limestone 
Water  rock  


0-  3 

3-  5 

5-  65 

65-  215 
215-  288 
288-  392 
392-  402 
402-  455 
455-  485 
485-  542 
542-  590 
590-  600 
600-  636 
636-  680 
680-  702 


The  Del  Rio  in  this  well  lies  at  547  feet  from  the  surface.  An- 
other well  on  this  property  located  375  feet  west  of  the  one  re- 
ported reached  the  Del  Rio  at  590  feet  or  43  feet  lower  than  in 


the  first  well.  Aside  from  this  difference  in  level,  the  formations 
are  much  the  same  in  the  two  wells.  By  reference  to  the  struc- 
tural map  it  will  be  seen  that  these  wells  are  located  but  a short 
distance  north  of  the  large  fault  which  passes  between  the  wells 


and  the  Castroville  Road. 


98.  Salado  Water  Supply  Company,  % mile  south  of  Austin 
Road,  about  5 miles  northeast  of  San  Antonio,  on  Salado  Creek. 
Jacob  Wolff,  driller.  6000  gallons  water  per  minute. 


Surface  0-  8 

Dark  blue  clay  8-  108 

Light  blue  clay 108-  215 

White  rock,  soft  215-  330 

Yellow  rock,  sulphur  water 330-  350 

White  chalk,  hard  350-  445 

Lignite  (Eagleford)  445-  470 

White  rock,  hard  470-  510 

White  pearl  rock  510-  520 

Blue  hard  rock  520-  540 


Geology  and  Mineral  Resources  of  Bexar  County 


161 


Sand  hole  540-  585 

White  rock,  hard  585-  610 

Red  sand  rock,  gas  flow  610-  617 

Hard  white  rock  617-  642 

Brown  flint  642-  647 

Yellow  water  rock,  white  streaks 647-  702 


99.  San  Antonio  and  Aransas  Pass  Railway,  at  “roundhouse”  on 
railway  near  the  intersection  of  Proban  and  Simpson  streets,  west 
of  the  San  Antonio  River,  near  intersection  of  S.  P.  Ry.  and  S.  A. 
& A.  P.  Ry.  south  of  San  Antonio.  Allen  Burman,  driller.  Sulphur 
water  was  obtained  from  the  Austin  at  620  feet,  from  the  surface; 
good  water  was  obtained  at  1065  and  at  1090  feet.  The  water  is 
reported  to  rise  50  feet  above  the  ground  level.  The  Del  Rio  clay 
in  this  well  lies  at  270  feet  below  sea  level.  Casing,  7 V2 " to  550 
feet.  The  Del  Rio  is  cased  off  by  70  feet  of  6^"  casing. 


Soil  0-  6 

Soft  white  clay  6-  22 

Sticky  yellow  clay 22-  80 

Hard  blue  clay  30-  100 

Soft  blue  clay  100-  250 

Hard  gray  clay  250-  300 

Soft  white  soapstone  300-  350 

Hard  blue  clay  350-  400 

Soft  white  clay  400-  500 

Hard  white  rock  500-  550 

Hard  white  rock  550-  600 

Soft  gray  rock,  sulphur  water  at  620' 600-  700 

Hard  gray  rock 700-  750 

Hard  white  rock  750-  850 

Hard  brown  rock  850-  900 

Hard  blue  sea  mud  (Del  Rio) 900-  950 

Hard  white  limestone  950-1103 


101.  San  Antonio  City  Water  Supply,  about  400  yards  west  of 
Concepcion  Mission,  south  San  Antonio.  A second  well  drilled  about 
200  .feet  north  of  this  one  records  only  about  7 feet  of  Del  Rio, 
entered  at  1270  feet.  The  reduced  thickness  of  the  Del  Rio  to- 
gether with  the  abrupt  dip  probably  indicates  faulting  at  this 
locality  with  the  downthrow  to  the  south.  Surface  elevation  of 
this  well  about  605  feet.  Water  in  completed  well  rises  72  feet 
above. floor  of  derrick,  or  to  elevation  of  680  feet. 


Surface  materials  0-  54 

Blue  clay  54-  7 80 

“Magnesian”  limestone  780-  900 

10"  pipe  rested  at  800 


11  -Bex. 


162 


University  of  Texas  Bulletin 


Gray  limestone  905-1197 

Water  at  1130. 

Lignite  (Eagleford)  1197-1223 

Limestone  with  crevices  and  water  flowing  at 

surface  3000  gals,  per  min 1223-1280 

Mud  (Del  Rio)  1287-1328 

Limestone  with  crevices  and  water  1323-1440 

102.  San  Antonio  City  Water  Supply,  Market  Street.  Surface 
elevation  about  660  feet.  Actual  level  top  of  Del  Rio,  725. 

Surface  materials  0-  35 

Blue  clay  •.'...  35-  220 

Hard  rock  220-  375 

“Magnesian”  rock  375-  500 

Sulphur  water  at  505 

Lignite  (Eagleford)  600 

Buda  not  given 

“Mud”  (Del  Rio)  725-  775 

Limestone  rock  775-  887 

Water  mostly  at 860-  88  5 


103.  San  Antonio  City  Well,  north  city  limits  on  San  Antonio 
River.  Benkendorfer,  driller.  This  well  starts  in  the  Austin  al- 
though as  the  record  indicates,  within  about  100  feet  of  the  base  of 
this  formation.  The  Eagleford  is  thin,  apparently  only  about  15 
feet  thick.  By  reference  to  the  map  it  will  be  seen  that  this  well  is 


located  very  close  to  a large  fault. 

Mud  and  soil  0-  12 

Rock  12-  21 

Yellow  rock  21-  65 

Blue  rock  65-  73 

Yellow  rock 73-  82 

Brown  rock  82-  87 

Blue  rock  87-  96 

Yellow  rock 96-  101 

Brown  lignite  (Eagleford) 101-  116 

Yellow  hard  rock  116-  144 

White  hard  rock 144-  149 

Gray  hard  rock  149-  17  3 

Blue  mud  (Del  Rio) 173-  234 

Yellow  water  rock,  very  hard;  some  flint  to  bottom 

of  well  234-  702 


Principal  water  supply  at  650-670  feet;  water  rises  just  to  top 
of  pipe.  Does  not  flow  over. 


104.  San  Antonio  Portland  Cement  Company,  on  I.  & G.  N.  Ry.,  5 


Geology  and  Mineral  Resources  of  Bexar  County  1 63 

miles  northeast  of  San  Antonio.  Log  from  memory;  depth  of 


formations  approximate: 

Yellow  clay  0-  60 

Blue  hard  rock  . 60-  250 

White  and  yellow  limestones  250-  400 

Hor.ey-combed  hard  limestones  400-  450 

Lignite  (Eagleford)  450-  462 

Hard  yellow  limestone 462-  572 

Black  rock 572-  587 

Sea  mud  (Del  Rio) 587-  657 

Hard  limestones  657-  667 


This  record  given  to  the  writer  by  the  driller  from  memory  can 
be  used  only  as  an  approximate  statement  of  depths  to  the  forma- 
tions. Another  record  of  a well  at  this  locality,  from  notes  con- 
tributed by  Mr.  Deussen,  differs  somewhat,  placing  the  Del  Rio 
probably  nearer  the  surface.  The  uppermost  60  feet  in  this  well 
is  probably  the  Taylor  formation.  The  next  390  feet  is  to  be  re- 
ferred to  the  Austin  formation.  The  materials  recorded  as  lignite, 
hard  yellow  limestone,  and  as  black  rock  presumably  include  the 
Eagleford  and  Buda  formations,  giving  them  a combined  thick- 
ness of  122  feet.  The  Del  Rio,  “Sea  mud,”  is  recorded  as  having 
its  usual  thickness  of  70  feet.  The  well  is  here  recorded  as  entering 
the  Georgetown  at  657  feet,  this  formation  having  been  drilled  into 
only  about  10  feet. 


107.  George  Sauer,  Bulverde  Road,  near  Haags’  store,  6%  miles 
from  San  Antonio.  Alex  Lorenz,  driller. 

Limestone  (Austin)  0-  170 

Shales.  (Eagleford)  170-  210 

Limestone  (Buda)  210-  2 60 

Clay  (Del  Rio)  260-  330 

Limestones  (Georgetown)  330-  370 

108.  Henry  Shumeier,  1 mile  south  of  Wetmore,  west  side 

Bulverde  Road.  Lorenz,  driller.  Elevation  760;  non-flowing  ar- 
tesian water. 

Adobe  and  hard  rock  (Austin) 0-  250 

Lignite  (Eagleford)  250-  275 

Hard  rock  (Buda)  275-  325 

Mud  (Del  Rio)  325-  375 

Limestone  rock  375-  420 


109.  Shattuck  well,  on  19th  i Street,  about  1 mile  south  of  El- 
mendorf  Lake,  and  near  the  west  city  limits  of  San  Antonio.  L.  N. 


Knight,  driller. 

Chiefly  yellow  and  blue  clay 0-  335 

Limestone  ! 335-  703 


164  University  of  Texas  Bulletin 

Eagleford  703-  735 

Buda  735-  798 

Del  Rio  798-  850 

Limestones  856 

111.  Southern  Ice  Company,  Durango  and  Frio  streets,  east  of  I. 
& G.  N.  Ry.,  and  south  of  Commerce  Street,  San  Antonio. 

Soft  pebbles  0-  5 

Hard  pebbles 5-  8 

Yellow  clay  8-  4 8 

Brown  clay  48-  160 

Brown  clay,  light  160-  260 

Magnesian  rock 260-  385 

Lime  rock  385-  520 

Sulphur  water  at  428 

White  limestone  557 

Not  recorded  557-  566 

White  clay  566 

Not  recorded  566-  585 

“Coal”  (Eagleford)  585-600? 

“White  lime  (Buda)  600-  650 

“Mud”  (Del  Rio)  650-  711 

Limestone  (Georgetown-Edwards)  711-  911 

113.  Southwest  Land  Corporation,  abodt  300  yards  south  of 
Commerce  Street  and  1 mile  west  of  Lady  of  the  Lake  College, 
San  Antonio.  T.  H.  Little,  driller.  Sulphur  water  at  410  feet. 
Elevation,  708.  Good  water  at  715  and  850  feet. 

Gravel  and  yellow  clay  (Navarro-Taylor)  0-  60 

Shale  (Navarro-Taylor)  60-  390 

Soft  white  lime  (Austin)  : 390-  528 

Lignite  (or  shale)  (Eagleford) 528-  560 

Hard  white  lime  (Buda)  560-  620 

Mud  hole  (Del  Rio)  620-  672 

Light  brown  lime  (Georgetown-Edwards)  672-  700 

White  to  gray  lime  (Georgetown-Edwards)  700-1000 

118.  Steves  Irrigated  Gardens,  San  Antonio.  First  water  came 
to  top  at  1065-1070  feet.  Drilled  into  water  rock  at  1185  feet 
when  drilling  had  to  be  abandoned,  on  account  of  flow  of  water. 

Surface  materials,  water  0-  2 8 

Blue  clay  59-  604 

White  clay  or  rock 604-  728 

Gray  rock  728-  780 

Yellow  rock  780-  805 

Gray  rock  805-  894 


Geology  and  Mineral  Resources  of  Bexar  County  165 


Sulphur  water  850 

Lignite  (Eagleford)  894-  922 

Gray  rock  (Buda) 922-  983 

Mud  hole  (Del  Rio) 983-1041 

Gray  rock  1041-1060 

Water  at  1065 

Brown  rock  1060-1100 

Brown  hard  flint  1100-1140 

Gray  hard  flint?  1140-1160 

Yellow  hard  flint?  1160-1185 


119.  Steves  well,  509  King  William  St.,  San  Antonio.  Surface 
elevation  about  '650  feet.  First  sulphur  water  at  449;  big  flow 


at  742  feet. 

Surface  0-  2 

Hard  pan  8-  19 

Gravel  19_  34 

Yellow  clay  34_  42 

Blue  clay  42-  250 

Austin  chalk  . 250-  442 

White  limestone  442-  472 

Yellow  limestone  472-  489 

Gray  limestone  489-  580 

Lignite  (Eagleford)  580-  613 

Gray  limestone  61 3_  682 

Crystallized  lime 682-  734 

Total  depth  758 


120.  Steves  well,  south  of  Chavanaux  Road,  west  of  S.  A.  & A. 
P.  Ry.  Benkendorfer,  driller.  Flowing  warm  sulphur  water.  The 
Del  Rio  clay  in  this  well  although  not  very  definitely  placed  is 
reported  to  lie  1790  feet  from  the  surface,  or  at  the  level  1130 
feet  below  sea.  This  record  places  the  formation  nearly  400  feet 
lower  than  in  the  Alta  Vista  oil  field.  Scarcely  more  than  a mile  to 
the  east-southeast. 

Y/123.  Superior  Oil  Company,  Linn  farm,  east  of  Palo  Alto  Road, 
12  miles  south  of  San  Antonio.  Fitzgerald,  driller.  Test  well  for 
oil.  Oil  showings  as  noted.  Also  warm  flowing  sulphur  water 
from  the  Comanchean  formations. 


Black,  soil  and  clay 1_  14 

Yellow  clay  14_  ig 

Yellow  clay  18_  50 

Yellow  and  l}lue  clay 50-  80 

Blue  and  red  shale 80-  125 

shale  125-  145 


166  University  of  Texas  Bulletin 

Greensand  (set  178'  8"  pipe)  145-  168 

Tough  shale  168-  187 

Shale  and  slate  187-  263 

Gas  rock  263-  275 

Soft  lime  rock 275-  279 

Gas  sand,  hard  279-  282 

Shale  282-  320 

Lime  rock  320-  328 

Fine  sand  328-  335 

Shale  with  occasional  boulders 335-  420 

Soft  shale  and  white  slate 420-  500 

Shale  and  soft  slate 500-  750 

Soft  white  lime  750-  753 

Gypsum  and  shale  753-  758 

Soft  gray  lime  . . . . 758-  761 

Shale  761-  783 

Lime  and  shale  783-  796 

Lime  rock  and  pyrite  of  iron 796-  800 

Gypsum  and  shale 800-  830 

Lime  rock  830-  834 

Shale  834-  840 

Lime,  rock  840-  853 

Shale  853-  855 

Slate  855-  873 

Shale  ' 873-  904 

Slate  904-  909 

Shale  .1 909-  922 

Slate  / ...  922-  925 

Rock,  gray  limes 925-  926 

Blue  mud 926-  950 

Pyrites  of  iron  950-  953 

Rock,  lime 953-  980 

Oil-bearing  sand  980-  985 

Set  989  feet  of  6"  pipe 

Soft  shale  and  mud 985-1020 

White  shale,  strong  gas 1020-1060 

Oil-bearing  shale  1060-1088 

Rock,  gray  lime  1088-1125 

Shale  and  slate  1125-1200 

Lime,  soft  1200-1235 

Sand,  showing  little  oil .1235-1241 

Slate  and  shale  1241-1300 

Soft  shale,  caving 1300-1420 

Slate  1420-1430 

Soft  lime  1430-1439 

Shale  and  sand,  soft,  caving 1439-1500 


Geology  and  Mineral  Resources  of  Bexar  County  167 


Slate  and  shale 1500-1520 

Soft  blue  shale,  caving 1520-1557 

Set  4"  pipe 

Lime  rock  1557-1600 

Blue  slate  1600-1635 

Hard  white  lime 1635-1740 

Honey-combed,  soft  lime,  hot  sulphur  water 1740-1800 

Hard  and  soft  lime 1800-2  600 

Oil  sand,  small  showing  of  oil .2600-2606 

Hard  blue  lime 2606-2  900 

Little  sand  and  fresh  water  2900 


In  this  well  a greensand  horizon  is  reported  at  145  feet  from 
the  surface.  The  Del  Rio  clay  appears  from  the  log  to  lie  at 
about  1500  feet  from  the  surface,  the  interval  between  the  green 
sand  and  the  top  of  the  Del  Rio  here  being  1375  ft.  while  in  the 
Kearney  well  nearby  this  interval  appears  to  be  1326  feet.  When 
reduced  to  actual  elevations,  the  greensand  horizon  in  the  two 
wells  is  found  to  be  about  20  feet  higher  in  the  Kearney  than  in 
this  well.  The  well  was  drilled  approximately  1500  feet  into  the 
Comanchean  formations  and  hence  probably  terminates  in  the 
Travis  Peak  formation.  Although  not  so  stated  in  the  log,  one 
of  the  drillers  on  this  well  reports  that  near  the  bottom  of  the 
well  was  found  little  altered  wood  resembling  cedar,  similar  to 
that  found  in  the  Ridder  well. 

124.  Terrell  Plot  Wells,  west  of  the  Pleasanton  Road,  5 y2  miles 
south  of  San  Antonio.  Record  published,  in  U.  S.  G.  S.,  18th  Ann. 
Rpt.,  Pt.  2,  p.  294.  Flowing  warm  sulphur  water,  temperature 
reported  to  be  106°  F. 

From  the  record  of  this  well  it  appears  that  the  Del  Rio  clay 
was  passed  through  here  at  from  1380  to  1425  feet  or  at  the 
actual  level  of  750  feet  below  sea.  From  these  data  the  top  of  the 
Comanchean  formations  would  be  expected  at  about  1320  feet 
from  the  surface.  Accordingly  the  whole  of  the  Upper  Cretaceous 
and  possibly  some  of  the  Tertiary  is  penetrated  by  this  well.  At 
the  depth  of  600  feet  from  the  surface  were  fossils  identified  by 
Dr.  Hill  as  Gryphea  vesicularis,  indicating  the  Navarro  formation. 
Brown  coal,  or  lignite,  is  reported  in  this  well  at  140,  240,  and  280 
feet  from  the  surface.  The  lignite  suggests  that  the  Wilcox  may 
be  present,  extending  into  this  structurally  low  area  possibly  from 
the  southwest. 

125.  J.  H.  Terrell,  at  west  city  limits,  V2  mile  north  of  south 
limits  of  San  Antonio.  Sulphur  water  from  the  Austin  at  765 
feet;  good  water  at  1134  to  1140  feet. 


Gravel  and  yellow  clay  0-  60 

Shale  60-  550 

Soft  white  rock 550-  903 

Lignite  (or  shale)  (Eagleford 903-  938 

Hard  white  lime  (Buda) 938-  998 


168 


University  of  Texas  Bulletin 


Mud  hole  (Del  Rio) 998-1058 

Brown  and  white  lime 1058-1140 


127.  Louis  Tezel,  one  mile  north  Culebra  Road,  13  miles  north- 
west of  San  Antonio.  Goforth,  driller.  Actual  level  of  Del  Rio, 


715  feet. 

Rock,  not  hard  (Austin)  0-  55 

Lignite  (Eagleford)  55-  90 

Buda  90-  150 

Del  Rio  150-  210 

Rock  (Georgetown-Edwards)  210-  245 


132.  Townsite  well,  Somerset.  This  well  was  drilled  to  the 
depth  of  2002  feet  many  years  ago,  and  of  this  part  of  the  well  no 
log  has  been  found.  Showings  of  oil  were  reported  at  800-1100 
and  1400  feet.  During  the  summer  of  1919  the  well  was  deepened 
to  2320  feet  by  Dr.  F.  L.  Thompson.  From  2002  to  2030  feet  no 
record  has  been  made  altho  the  drilling  is  said  to  have  been  in 
rock  (Buda?).  Below  2030  the  samples  indicate  70  feet  of  light 
blue  clay.  Altho  no  fossils  were  found  this  clay  in  general  ap- 
pearance resembles  the  Del  Rio  formation.  Below  the  clay  from 
2100  to  2320  the  cuttings  indicate  limestones  varying  in  texture 
and  apparently  representing  the  Georgetown-Edwards  formations. 
The  well  terminated  in  strata  containing  a great  deal  of  pyrite. 

While  the  data  on  this  well  are  not  as  complete  as  desired  it  ap- 
pears probable  that  the  Del  Rio  formation  at  this  place  lies  from 
about  2030  to  2100  feet  from  the  surface.  The  elevation  at  the 
depot  at  Somerset  as  shown  by  the  profile  of  the  Artesian  Belt 
Railway  is  650  feet  above  sea.  The  elevation  at  the  well  altho  not 
accurately  determined  does  not  vary  greatly  from  that  at  the 
depot.  Accordingly  the  Del  Rio  is  placed  provisionally  at  this 
locality  as  lying  about  1380  feet  bslow  sea  level. 

135.  Union  Meat  Company,  south  Laredo  street,  between  Ralph 
and  Brazos.  Sulphur  water  at  491  feet;  good  water  at  1150  feet. 


Gravel  and  yellow  clay  0-  60 

Blue  shale  . . 60"  340 

White  limestone  340-  656 

Lignite  (or  shale)  (Eagleford) 656-  686 

Hard  white  limestone  (Buda) 686-  751 

Mud  hole  (Del  Rio) * 751-  820 

Light  brown  limestone 820-1150 

White  and  gray  limestone 1150-1400 

No  water  below  1250 


137.  Wm.  Yogt,  1 V2  miles  west  of  the  Medina  River  and  1/2 


Geology  and  Mineral  Resources  of  Bexar  County  169 


mile  north  the  Quintana  Road.  Flowing  warm  sulphur  water  from 
the  Conianchean  formations. 

In  this  well  the  greensand  was  reached  at  297  feet  from  the 
surface,  or  at  the  level  308  feet  above  sea.  The  Del  Rio  formation 
was  reached  at  about  1485  feet  and  was  found  to  be  52  feet  thick. 
Water  was  obtained  from  the  limestones  at  1560  feet  and  succes- 
sively thereafter  to  the  bottom  of  the  well,  1850  feet.  This  well 
was  drilled  into  the  limestones  below  the  Del  Rio  313  feet  and 
hence  teiminates  probably  in  the  Edwards  formation.  The  strati- 
graphic interval  from  the  glauconitic  greensand  to  the  top  of  the 
Del  Rio  is  here  given  as  about  1188  feet,  or  91  feet  less  than  in 
the  Ridder  well.  The  record  of  the  Ridder  well  is  probably  the 
more  reliable. 


138.  Mrs.  A.  Voight,  on  the  north  side>  of  Culebra  Creek,  14 
miles  from  San  Antonio  on  the  Culebra  Road.  This  well  is  lo- 
cated near  the  axis  of  the  large  structure  described  as  the  Culebra 


anticline. 

Surface  materials  and  rather  soft  rock  (Austin) 0-  35 

Lignite  (Eagleford)  35-  65 

Buda 65-  120 

Mud  hole  (Del  Rio) 120-  180 

Rock  (Georgetown-Edwards)  180-  216 

Actual  level  top  of  Del  Rio 730 


139.  Waiing  well,  on  south  side  Bandera  Road,  about 
miles  northwest  of  San  Antonio.  D.  Benkendorfer,  driller.  Non- 
flowing artesian  water  probably  from  the  Travis  Peak  formation. 


Soil 0-  3 

Gravel  3-  13 

Adobe,  lime  and  boulders  13-  70 

Blue  clay  70-  215 

Yellow  limestone  215-  23  0 

Crevice  230-  232 

White  limestone  232-  265 

Blue  clay  265-  275 

White  limestone  275-  295 

Blue  slate  295-  325 

Adobe  limestone  325-  335 

White  limestone  335-  370 

Lignite  (Eagleford)  370-  400 

White  limestone  (Buda) 400-  460 

“Mud  hole”  (Del  Rio) 460-  510 

White  limestone  510-  530 

Crevice  with  water 530-  532 

Yellow  limestone  532-  550 

Crevice  with  water 7 550-  555 


170  University  of  Texas  Bulletin 

White  limestone  555-  600 

White  limestone  600-  615 

Sand,  brown  limestone  and  water 615-  745 

White  limestone  745-  7 85 

Brown  limestone  785-  795 

White  limestone  795-  815 

Brown  limestone,  water 815-  830 

White  limestone  830-  865 

Brown  limestone,  water 865-  870 

White  limestone  . 870-  920 

Brown  limestone  920-  925 

White  limestone  925-  950 

Crevice,  brown  limestone 950-  955 

White  limestone  955-1035 

Brown  limestone  1035-1080 

Blue  limestone  1080-1190 

White  limestone  1190-1230 

Blue  limestone  1230-1260 

Blue  slate  1260-1262 

White  limestone  1262-1455 

Hard  brown  crystallized  limestone 1455-1478 

Blue  limestone  1478-1505 

Hard  brown  crystallized  limestone  1505-1510 

White  limestone  1510-1530 

Hard  blue  limestone  . . . 1530-1565 

Blue  limestone  1565-1580 

Brown  limestone  1580-1595 

White  limestone  1595-1635 

Hard  blue  limestone 1635-1655 

Brown  limestone,  white  hard  streaks 1655-1700 

Hard  blue  limestone  1700-1715 

Brown  limestone  1715-1735 

White  limestone  1735-1795 

Hard  brown  limestone  1795-1860 

Soft  gray  rock  1860-1870 

Hard  blue  ,mndy  rock 1870-1915 

No  description  1915-1935 

Mud  1935-1953 

White  limestone  1953-1985 

Mud  1985-1987 

White  limestone  1987-1997 

Mud  at  2000 

One  foot  of  mud  at 2008 

Hard  limestone,  shells  aild  mud  to 204  0 

Soft  white  limestone  2040-2070 

Very  hard  sandy  limestone 2070-2100 


Geology  and  Mineral  Resources  of  Bexar  County  171 


White  limestone  . -. 2100-2115 

Mud  2115-2140 

Limestone  ..2140-2100 

Blue  mud 2190-2483 

Hard  limestone,  streaks  of  mud  2483-2600 

White  sand  2600-2645 

White  limestone  ...2645-2675 

Dark  limestone  and  sand  2675-2699 

Trinity  white  sand,  water 2699-2705 

Very  hard  cap  rock 2705-2711 

Sand  and  hard  streaks 2711-2784 

Sondstone,  very  hard,  filled  with  red  mud  2784-2810 

Crevice  281 0-2  813 

Sandstone  shale  2813-2853 


This  well  is  of  interest  as  affording  apparently  the  maximum 
thickness  thus  far  recorded  for  the  Comanchean  formations  in 
this  county.  The  Buda  limestone  was  entered  at  400  feet  from 
the  surface,  and  while  no  cuttings  were  preserved,  it  would  appear 
from  the  log  that  the  Cretaceous  extends  to  2705  feet,  if  not  to  the 
full  depth  of  the  well.  Assuming  the  base  of  the  Cretaceous  to  lie 
at  2705  feet  there  is  indicated  a thickness  of  the  Cretaceous  of  not 
less  than  2300  feet.  The  age  of  the  materials  from  2705  feet  to 
the  bottom  of  the  well.  2853,  is  in  doubt.  Dirt  taken  from  the 
dump  around  the  well  when  washed  and  examined  failed  to  show 
the  presence  of  schists  such  as  were  found  below  the  Cretaceous 
farther  to  the  north,  altho  this  test  can  not  be  -assumed  to  be  con- 
clusive as  to  the  presence  or  absence  of  schists. 

WELLS  TERMINATING  IN  THE  UPPER  CRETACEOUS 

Among  wells  terminating  in  the  Upper  Cretaceous  the  fol- 
lowing are  listed  as  indicative  of  conditions  met  with  in  drill- 
ing into  these  formations.  The  wells  entering  the  Comanchean 
as  already  noted,  are  chiefly  water  wells,  while  those  of  the 
Upper  Cretaceous  are  chiefly  either  oil-producing  wells  or 
wells  drilled  in  testing  for  oil  or  gas. 

145.  Cohen  & Roby,  north  of  and  near  to  the  jog  in  the  Dwyer 
cross  road  in  the  Gas  Ridge  oil  and  gas  field.  Depth,  1035  feet, 
Elevation  about  750  feet.  Showings  of  gas  between  170  and  249 
feet,  large  gas  production  865-990;  showings  of  oil  at  480,  492,  550, 
615,  780,  815,  and  1000-1035. 


Gravel  0-  10 

Yellow  clay  10-  9 0 

Black  shale  90-  100 


172  University  of  Texas  Bulletin 

Blue  shale  100-  120 

Light  blue  shale 120-  100 

Dark  blue  shale  160-  170 

Shelly  rock,  gas 170-  240 

Blue  shale 240-  400 

Small  shell  rock,  first  oil 400-  444 

Sand  6 inches 444-  450 

Blue  shale. 450-  460 

Shell  of  rock,  oil  sand 460-  475 

Oil  sand  475-  498 

Blue  shale  .* 498-  500 

Shell  of  rock,  oil  sand 500-  550 

Blue  shale  6 inches  . ^ 550-  570 

Small  shell  rock,  oil  sand  6 inches  57  0-  615 

Shell  rock  : . 615-  650 

Blue  shale  650-  700 

Shell  rock,  more  oil  sand 700-  780 

Blue  shale  780-  800 

Small  shell  rock,  more  showing  of  oil 800-  815 

Shell  rock  and  gas 815-  840 

Blue  shale 840-  850 

Large  shell  rock,  large  gas 850-  865 

Gas  rock  865-  890 

Gas  rock  890-  990 

Blue  shale  990-1000 

Oil  sand  1000-1035 

This  well  starts  in  the  Navarro  formation  and  probably  ter- 
minates in  the  Austin  formations.  The  large  gas  supply  at  about 
850  feet  is  probably  in  the  Taylor  formation.  The  heavy  oil  from 
this  well  at  the  depth  of  1035  feet,  analysis  of  which  has  been 
given,  is  probably  from  the  Austin  formation. 

14  6.  Crosby  well  No.  4,  in  Bexar  County,  north  of  Somerset. 

Soil  1-  16 

Rock  16-  20 

Black  gumbo 20-  60 

Rock  60-  62 

Shale  62-  92 

Water  sand  92-  107 

Gumbo  107-  132 

Shale  132-  262 

Rock  262-  265 

Gumbo  265-  275 

Water  sand  275-  293 

Gumbo  293-  343 

Rock  343-  34  7 

Gumbo  347-  382 


Geology  and  Mineral  Resources  of  Bexar  County  173 


Shale  382-  482 

Gumbo  482-  552 

Soft  shale  552-  602 

Gumbo  - 602-  682 

Soft  sandy  shale 682-  742 

Hard  sandy  shale,  shell  of  rocks  742-10  20 

Very  hard  rock  1020-1022 

Sand  shale  1022-1048 

Rock 1048-1051 

Shale  and  gumbo  1051-1116 

Shale  1116-1126 

Gumbo  1126-1141 

Shale  1141-1181 

Gumbo  1181-1191 

Shale  1191-1217 

Rock  1217-1231 

Shale  and  oil  sand  1231-1251 

Gumbo  1251-1254 


As  in  the  case  of  other  wells  in  the  Somerset  field,  in  Bexar 
County,  this  well  starts  in  the  Wilcox  formation.  The  formation  in 
which  it  terminates  and  from  which  oil  is  obtained  is  not  definitely 
determined  but  is  assumed  to  be  either  the  Navarro  or  the  Taylor. 

14  7.  Ingram  well  in  the  Alta  Vista  Field,  drilled  1905,  Jacob 
Wolff,  driller.  Depth,  1120  feet;  6"  casing  set  at  960  feet. 

Greensand  stratum  recognized  at  260  feet 30  ft.  thick 

This  stratum  according  to  Wolff  made  a barrel  of  oil  per  day, 
gravity  32  (some  other  tests  reported  the  gravity  38). 

Second  stratum  greensand  at  700  or  740  feet,  about.  .70  ft.  thick 

Contained  a good  deal  of  gas  and  some  oil.  Made  2 y2  to  3 bar- 
rels per  day. 

Austin  chalk  rock  recognized  at  1000  ft. 

Heavy  Alta  Vista  oil  found  at  1060  to  1080  ft.  This  heavy  oil 
from  a 5 or  6 foot  crevice  in  the  rock  containing  asphalt  like 
material. 

Although  not  a procjucing  well,  this  well  is  of  interest  as  the 
first  well  drilled  within  the  Alta  Vista  field  in  which  a pronounced 
showing  of  oil  was  obtained.  The  well  was  drilled  for  water.  The 
first  producing  oil  well  in  this  field  was  drilled  about  ten  years  later. 

14  8.  Wells  of  the  Kimbly  and  Brown  lease  on  the  Swearingen 
property,  south  of  the  Medina  River. 

The  producing  horizon  is  reported  in  the  wells  on  this  property 
at  the  following  depths:  Swearingen  No.  1,  located  at  north  side 

of  the  property,  producing  sand  at  from  1210  to  1235  ft;  Swear- 
ingen No.  2,  producing  sand  at  from  1216  to  1245  ft;  Swearingen 
No.  3,  producing  sand  at  from  1248  to  1280  ft;  Gale  No.  1,  produc- 


174 


University  of  Texas  Bulletin 


ing  sand  at  from  1360  to  1400  ft;  Swearingen  No.  4,  producing 
sand  at  from  1425  to  1485  ft.  The  wells  are  listed  in  the  order 
of  their  location  from  north  to  south  or  east  of  south.  The  dip 
of  the  formations  is  thus  seen  to  amount  to  as  much  as  115  feet 
between  wells  No.  1 and  No.  4.  The  distance  between  these  wells 
is  a little  more  than  a mile. 

These  wells  start  in  the  Tertiary.  The  formation  in  which  they 
terminate  is  undetermined  but  may  be  either  the  Navarro  or  Taylor, 

The  following  log  is  of  the  Nimbly  and  Brown  Swearingen  No. 
4.  This  is  the  southernmost  and  deepest  of  the  five  wells  drilled  in 
this  field  to  the  close  of  1918.  Log  furnished  by  Mr.  Brown. 


Soil  0-  3 

Red  clay  3-  27 

Yellow  clay  27-  50 

Sand  50-  80 

Lignite  80-  81 

Sand  81-  140 

Streaks  of  lignite  140-  146 

Sand  146-  200 

Rock  200-  208 

Sand  208-  317 

Rock  • 317-  323 

Brown  gumbo  323-  386 

Rock  386-  394 

Shale,  thin  rocks  394-  490 

Gumbo  496-  575 

Rockj  575-  581 

Shale  58 1“  750 

Rock  750-  752 

Gumbo  ' 752-  880 

Black  sand,  gas 880_  900 

Gumbo  900-1395 

Soft  rock  shows  some  lime 1395-1425 

Oil  sand  1425-1458 

Gumbo  1458-1462 


14  9.  Well  of  J.  K.  Lamb,  drilled  by  Park  Oil  and  Gas  Co.,  west 
of  Corpus  Christi  Road,  about  2 miles  south  of  the  Medina  River. 


Test  well  for  oil. 

Surface  sand  2 

Red  sandy  clay 2-  20 

Water  sand  and  boulders  29_ 

Loose  gumbo  and  boulders  112-  150 

Gumbo  150-  160 

Sand  rock  160-  165 

Gumbo  165-  172 


Geology  and  Mineral  Resources  of  Bexar  County  175 


Sand  rock  

Sandy  gumbo  

Sand  rock  

Gumbo  (Set  8"  pipe  at  265  ft.) 

Hard  sand  rock  

Gumbo  

Sandy  gumbo  

Sandy  gumbo  

Sand  rock  

Water  sand  

Sand  rock  

Sandy  gumbo  and  boulders  . . . . 

Shale  and  gumbo  

Hard  rock  and  gumbo 

Sand  rock  

Shale  and  boulders 

Sand  rock  

Shale  

Hard  rock  

Shale  

Sand  and  lime  rock 

Shale  

Sand  rock  

Shale  

Sand  rock  . 

Shale  

Sand  rock  

Shale  

Sand  rock  

Hard  shale 

Sand  rock  

Shale  

Sand  rock  

Shale  and  rock  

Gumbo  

Sand  rock  . 

Shale  and  gumbo  

Sand  rock  

Shale  and  boulders 

Gumbo  . 

Sand  rock  

Shale  

Gumbo  (Set  6"  pipe  at  1118  ft) 

Coarse  shale  

Fine  shale  

Shale  (slight  showing  of  oil) 


. 172-  174 
. 174-  222 
. 222-  227 
. 227-  342 
. 342-  362 
. 362-  388 
. 388-  392 
. 392-  450 
. 450-  453 
. 453-  460 
. 460-  465 
. 465-  505 
. 505-  565 
. 565-  582 
. 582-  587 
. 587-  701 
. 701-  704 
, 704-  708 
. 708-  711 
, 711-  720 
, 720-  723 
, 723-  747 
. 747-  751 
, 751-  790 
. 790-  793 
793-  800 
. 800-  803 
. 803-  811 
, 811-  815 
, 815-  850 
, 850-  853 
853-  860 
860-  863 
863-  940 
940-*  980 
980-  983 
983-  987 
987-1000 
1000-1030 
1030-1046 
1046-1048 
1048-1095 
1095-1110 
1110-1160 
1160-1190 
1190-1309 


176  University  of  Texas  Bulletin 

w 

Rock  1309-1313 

Shale  1313-1375 

Gumbo  1375-1385 

Shale  1385-1450 

Rock  1450-1453 

Shale  1453-1510 

Gumbo  1510-1535 

Rock  1535-1538 

Shale  (Set  4"  pipe  at  1555  ft)  1538-1600 

White  lime  1600-1620 

Shale  1620-1638 

Rock  1638-1641 

Shale  . 1641-1661 

Rock  1661-1662 

Shale  1662-1740 

Rock  1740-1742 

Shale  1742-1900 

Black  shale  1900-1940 

Sand  and  shale  1940-1980 


This  well  starts  in  the  Wilcox  formation.  The  Austin  forma- 
tion would  seem,  so  far  as  can  be  judged  from  the  log,  to  have 
been  entered  at  about  1600  feet  from  the  surface.  Allowing  for 
the  Taylor  and  Navarro  formations  their  usual  combined  thickness 
of  about  900  feet,  there  is  indicated  at  least  700  feet  of  Tertiary  at 
this  locality.  The  Austin  formation  apparently  is  300  feet  thick, 
the  Eagleford  “black  shales”  having  been  entered  at  1900  feet. 
Cuttings  from  this  well  were  examined  at  the  time  the  well  was 
drilled,  by  Dr.  J.  A.  Udden,  who  identified  the  Austin  formation  as 
extending  from  about  1600  to  1900  feet  and  the  Eagleford  below 
1900  feet.  If  this  well  terminates  in  the  Eagleford  at  1280,  as 
seems  probable  from  both  the  log  and  the  cuttings,  there  is  here 
the  maximum  thickness,  80  feet,  recorded  for  this  formation  in 
Bexar  County.  Assuming  that  the  well  terminates  at  or  near  the 
base  of  the  Eagleford,  the  estimated  level  of  the  top  of  the  Del 
Rio  at  this  place  is  somewhat  more  than  2000  feet  from  the  surface, 
or  near  1500  below  sea  level. 

150.  Mars  Discovery  well,  Alta  Vista  oil  field.  Elevation,  600 
feet.  Drilled  in  1915,  on  Kelso  tract,  8 miles  south  of  San  Antonio. 


Surface  0-  2 

Gravel  2-  4 

Red  clay  4-  16 

Joint  clay  16-  40 

Rock  lime  40-  46 

Yellow  sand  4 6-  54 

Blue  shale  5 4-  70 


Geology  and  Mineral  Resources  of  Bexar  County  177 


Sand  rock,  red 70-  72 

Blue  shale  72-  110 

Sand  rock,  rough  110-  113 

Blue  gumbo 113-  133 

Sand,  showed  oil  133-  160 

Blue  gumbo  160-  180 

Lime  shale,  hard  180-  325 

Rock,  lime  shell  32  5-  326 

Blue  gumbo  v 326-  340 

Blue  shale 340-  380 

Rock,  showed  pyrites 380-  400 

Hard  blue  shale  400-  436 

Blue  gumbo  436-  450 

Hard  blue  shale  450-  470 

Sand,  hard  and  black 4 70-  482 

Hard  blue  shale  482-  550 

Blue  gumbo  550-  590 

Hard  blue  shale  590-  655 

Blue  gumbo 655-  691 

Hard  blue  shale  691-  715 

Blue  gumbo 715-  763 

Soft  sand,  showed  oil 7 63-  780 

Soft  blue  shale  . . : 780-  808 

Sand,  showed  oil 808-  818 

Blue  gumbo  818-  840 

Hard  blue  sand 840-  851 

Blue  shale  851-  875 

Blue  gumbo 875-  890 

Lime  rock  890-  891 

Soft  blue  shale  891-  90  8 

Soft  sand  rock 908-  911 

Sand,  showed  oil  911-  915 

Blue  hard  shale 915-  9 40 

Blue  lime  rock  94 0-  941 

Gray,  hard  sand  941-  946 

Hard  blue  shale  946-  995 

Blue  gumbo 995-1010 

Sand,  showed  oil  1010-1014 

Soft  blue  shale  1014-1030 

Hard,  gray  sand  1030-1033 

Blue  gumbo  1033-1050 

Hard  gray  sand 1050-1058 

Hard  blue  shale  1058-1070 

Oil  sand,  hard  .1070-1090 

(Did  not  drill  to  bottom  of  oil  sand) 


12-Bex. 


178 


University  of  Texas  Bulletin 


151.  Mathey  No.  1 of  the  Bexar  Petroleum  Company,  located  on 
the  J.  H.  Mathey  property  about  one  mile  west  of  Losoya.  Eleva- 
tion 515  feet.  Depth  29  2 5. 

Notes  on  this  well  supplied  by  Hamilton  and  Walker  have  been 
included  in  connection  with  a discussion  of  the  thickness  of  the 
Midway  and  Wilcox  formations,  which  appear  to  extend  to  the  depth 
of  between  1340  and  1402  feet.  The  driller  believes  that  the 
Austin  formation  was  reached  at  the  depth  of  189  2 feet  and  con- 
tinued to  the  bottom  of  the  well,  2025.  I£  the  top  of  the  Austin 
be  placed  at  1892  feet,  and  from  the  drillers  log  apparently  it  can 
not  be  nlaced  at  any  higher  level,  the  Del  Rio  formation  is  to  be 
expected  in  this  well  at  a depth  approximating  2342  feet,  or  near 
the  actual  level  of  182  7 feet  below  sea.  The  seemingly  great  thick- 
ness of  the  Tertiary  in  this  well  and  in  the  Sarah  Smith  well,  log  of 
which  is  given  later,  indicates  that  a part  of  the  interval  assigned 
to  the  Upper  Cretaceous  in  the  Ridder,  Kearney,  and  Superior  Oil 
Co.  wells  may  possibly  also  be  Tteriary. 

LOG  OF  J.  H.  MATHEY  WELL  NO.  1 

Bexar  Petroleum  Company,  near  Losoya,  Bexar  County,  Texas. 
Elevation  515  feet.  Commenced  drilling  Nov.  18th.,  1919. 

0-  68  feet,  red  clay  and  small  gravel. 

68-  7 4 feet,  blue-gray  sand  rock. 

74-  78  feet,  black  gumbo. 

78-  80  feet,  blue-gray  sand  rock. 

80-  100  feet,  red  clay  and  small  gravel. 

100-  102  feet,  blue-gray  sand  rock. 

102-  130  feet,  red  clay  and  sand. 

130-  135  feet,  black  gumbo. 

135-  180  feet,  red  gumbo  and  hard  sand  (water). 

180-  190  feet,  black  gumbo. 

190-  201  feet,  black  shale. 

201-  208  feet,  black  gumbo. 

208-  222  feet,  dry  brown  sandy  shale. 

222-  224  feet,  brown  sand  rock. 

22  4-  240  feet,  black  gumbo. 

24  0-  260  feet,  dry  brown  sandy  shale. 

2 60-  263  feet,  shell. 

263-  290  feet,  dry  brown  sandy  shale. 

290-  293  feet,  brown  sand  rock. 

293-  330  feet,  brown  sandy  shale  (dry  and  hard). 

330-  336  feet,  black  gumbo. 

336-  350  feet,  brown  sandy  shale  (dry  and  hard). 

350-  358  feet,  black  gumbo. 

358-  359  feet,  gray  sand  rock. 


Geology  and  Mineral  Resources  of  Bexar  County 


359-  365  feet,  black  sandy  gumbo. 

365-  367  feet,  gray  sand  rock. 

367-  385  feet,  black  shale  with  lignite. 

385-  409  feet,  black  sandy  gumbo. 

409-  445  feet,  gray  sand  rock  (water)  (used  roller  bit) 

445-  465  feet,  black  gumbo. 

465-  466  feet,  gray  sand  rock. 

466-  471  feet,  black  sandy  gumbo. 

4 71-  472  feet,  gray  sand  rock. 

472-  505  feet,  black  sandy  gumbo  and  boulders. 

505-  515  feet,  black  shale. 

515-  519  feet,  gray  sand  rock. 

519-  557  feet,  black  sandy  gumbo  and  small  boulders. 

557-  570  feet,  black  shale  and  lignite. 

570-  574  feet,  gray  sand  and  lime  rock. 

574-  590  feet,  black  shale  and  lignite. 

590-  640  feet,  black  gummy  shale. 

640-  645  feet,  black  gummy  shale  and  boulders. 

645-  730  feet,  black  hard  gummy  shale. 

730-  740  feet,  black  soft  shale. 

740-  770  feet,  black  hard  gummy  shale.  (Some  fossils). 

770-  815  feet,  black  hard  gummy  shale. 

815-  819  feet,  black  soft  coarse  shale,  with  green  marl. 

819-  841  feet,  black  hard  gummy  shale. 

841-  850  feet,  black  soft  coarse  shale. 

850-1084  feet,  black  hard  gummy  shale.  921-928.  Core  No.  1 

1084- 1085  feet,  gray  hard  sand. 

1085- 1090  feet,  black  hard  gummy  shale. 

1090-1097  feet,  black  hard  gummy  shale. 

1097-1117  feet,  black  hard  gummy  shale. 

1117-1124  feet,  black  hard  sandy  shale. 

1124-1127  feet,  black  hard  gummy  shale. 

1127-1129  feet,  gray  sand  rock. 

1129-1165  feet,  black  hard  gummy  shale. 

1165-1170  feet,  brown  hard  sandy  shale. 

1170-1200  feet,  black  hard  gummy  shale. 

1200-1202  feet,  gray  sand  rock. 

1202-1214  feet,  black  hard  gummy  shale. 

1214- 1215  feet,  gray  sand  rock  with  pyrites. 

1215- 1360  feet,  black  hard  gummy  shale  (Core  1320-1322)  No.  2. 
1360-1372  feet,  black  hard  sandy  shale. 

1372-1407  feet,  black  hard  gummy  shale  (Core  1402-1406)  No.  3. 
1407-1417  feet,  black  soft  shale. 

1417-1472  feet,  black  hard  gummy  shale  (Core  1457-1459)  No.  4. 
1472-1490  feet,  gray  shale  with  lime.  (Lime  only  thin  layers). 
1490-1548  feet,  gray  hard  gumbo. 


180 


University  of  Texas  Bulletin 


1548-1556  feet,  gray  hard  shale. 

1556-1570  feet,  gray  hard  gumbo. 

1570-1582  feet,  gray  hard  shale. 

1582-1600  feet,  gray  hard  gumbo. 

1600-1622  feet,  gray  soft  shale. 

1622-1632  feet,  gray  hard  gumbo. 

1632-1670  feet,  gray  soft  shale.  (Gas  and  little  oil  showing). 
1670-1710  feet,  gray  hard  gumbo. 

1710-1720  feet,  black  soft  gummy  shale. 

1720-1740  feet,  gray  hard  gumbo. 

1740-1763  feet,  black  hard  gummy  shale.  (Core  1760-1763)  No.  5. 
1763-1820  feet,  black  hard  gummy  shale. 

1820-1825  feet,  black  soft  gummy  shale. 

1825-1840  feet,  black  hard  gummy  shale. 

1840-1845  feet,  black  soft  shale. 

1845-1861  feet,  gray  hard  sandy  gumbo. 

1861-1862  feet,  gray  lime  rock. 

1 862-1870  feet,  gray  hard  sandy  gumbo. 

1870-1885  feet,  gray  soft  shale. 

1885-1892  feet,  gray  hard  sandy  shale.  (Set  6-inch  easing  at  1892), 
1892-1938  feet,  blue-gray  chalk.  (Showing  little  gas  and  oil). 
1938-2007  feet,  blue-gray  chalk. 

152.  National  Oil  Co.,  Alta  Vista  oil  field:  Depth,  1132;  eleva- 
tion, 585.  Producing  horizon,  Austin  formation,  1120;  sulphur 
water  encountered  at  1132.  Actual  level,  top  of  producing  sand,  635 
feet  below  sea  level.  Estimated  position  top  of  Del  Rio  clay,  835 
feet  below  sea  level. 

153.  Oliver  well,  9^  miles  southwest  of  San  Antonio.  Depth 
1030  feet.  Oil  showing  at  200  and  at  600  feet.  Strong  gas  flow 
at  800  feet.  Gas  flow  reported  to  have  been  350,000  cu.  ft.  per  day 
at  time  well  was  drilled,  subsequently  probably  reduced  in  flow. 
This  well  probably  reached  to  the  Austin  formation;  however,  the 
showing  of  oil  and  the  gas  with  little  doubt  is  from  the  Taylor  and 
Navarro  formations. 

154.  Openheimer  well  No.  1.  Alta  Vista  field,  about  1400  feet 
northeast  of  Fuchs,  No.  1.  Smith,  driller.  Depth  1295  feet;  eleva- 
tion 620.  About  500  feet  east  of  the  Pleasanton  Road.  Producing 
horizon  at  1150  feet.  Sulphur  water  at  1295  fe«t.  Actual  level 
producing  sand,  530  feet  below  sea.  Estimated  place  of  the  Del  Rio 
830  feet  below  sea. 

155.  Park  Oil  and  Gas  Co.  Applewhite  No.  1 well.  North  side 
of  Rockport  Cross-road,  1 V2  miles  east  of  Applewhite  Road,  16 


Geology  and  Mineral  Resources  of  Bexar  County  181 


miles  south  of  San  Antonio  on  south  side  of  T.  C.  Applewhite  prop- 
erty. Thompson,  driller.  Depth,  1952  feet.  Elevation  500  feet, 


more  or  less.  Test  well  for  oil. 

Clay  0-  50 

Rock  50-  51 

Sand  51-  60 

Rock  60-  62 

Sand  and  boulders  62-  80 

Rock  80-  82 

Sand  : 82-  90 

Rock 90-  98 

Sand  and  boulders  98-  120 

Rock  120-  122 

Sand  and  boulders 122-  150 

Rock  150-  152 

Hard  sand  152-  200 

Rock  200-  202 

Sand  and  boulders  202-  240 

Shale  240-  275 

Packed  sand  275-  280 

Shale  and  boulders 280-  340 

Packed  sand  and  gravel 340-  370 

Packed  sand  370-  400 

Rock  400-  405 

Shale  405-  420 

Rock  420-  421 

Rock  (water  sand)  421-  542 

Sand  rock  542-  630 

Shale  630-  675 

Rock  675-  685 

Gumbo  685-  706 

Rock  706-  715 

Gumbo  715-  740 

Shale  and  boulders  740-  825 

Gumbo  825-  885 

Shale,  boulders,  oil  and  gas  sand 885-  940 

Gumbo  940-  972 

Hard  shale  972-  995 

Gumbo  995-1011 

Shale  .1011-1020 

Gumbo  ........ 1020-1030 

Hard  shale 1030-1036 

Gumbo  and  boulders  . . . .* 1036-1048 

Shale  1048-1050 

Shale  and  boulders,  showing  oil 1050-1080 

Gumbo  1080-1110 


Gumbo 


11  IQ-1127 


• 182 


University  of  Texas  Bulletin 


Rock 1127-1133 

Gumbo  1133-1148 

Rock  (red  sand  and  iron)  1148-1155 

Shale  and  oil  sand,  showing  oil 1155-1175 

Gumbo  1175-1185 

Rock  1185-1187 

Hard  shale  1187-1258 

Gumbo  1258-1262 

(Set  1261  ft.  6"  line  pipe  in  cement) 

Gumbo  1262-1268 

Hard  shale 1268-1290 

Soft  shale  1290-1380 

Gumbo  1380-1390 

Shale  and  boulders 1390-1425 

Gumbo  1425^1435 

Shale  and  boulders 1435-147  2 

Hard  sand  1472-1491 

Gumbo  1491-1512 

Hard  rock  1512-1514 

Shale  showing  oil 1514-1524 

Gumbo  1524^1530 

Rock  1530-1532 

Chalk  rock  1532-1572 

Gumbo  1572-1598 

Shale  and  oil  sand  (showing  oil  and  gas 1598-1645 

Gumbo  1645-1655 

Shale  1655-1688 

Gumbo  1688-1710 

Hard  shale  1710-1715 

Gumbo,  white  1715-1720 

Shale  showing  oil 1720-1730 

Gumbo  (Set  3"  lines)  1730-1732 

Shale  (Oil  show)  1732-1796 

Shale  1796-1809 

Dark  brown  sand  and  shale  (Oil  show)  1809-1816 

Shale  1816-1827 

Sand  1827-1830 

Gumbo  1830-1842 

Soft  shale  1842-1847 

Gumbo  1847-1852 

Soft  shale  1852-1857 

Gumbo  1857-1862 

Shale  and  hard  sand  1862-1867 

Gumbo  1867-1874 

Shale  1874-1877 

Gumbo  1877-1886 

Soft  rock  1886-1889 


Geology  and  Mineral  Resources  of  Bexar  County  183 


Soft  shale 1889-1896 

Chalk  rock  1896-1915 

Chalk  rock 1915-1934 

Oil  sand 1934-1952 

The  well  starts  probably  in  the  Wilcox  formation  and  to 
the  depth  of  1050  feet  or  more  may  be  Tertiary,  although  one 
cannot  be  sure  of  this.  The  reference  is  chiefly  because  of 
the  reported  presence  of  boulders  to  that  dpth.  From  1050 
to  1896  feet,  so  far  as  can  be  judged  from  the  log,  the  Navarro 
and  Taylor  formations  may  very  well  be  represented,  their 
combined  thickness  being  early  900  feet.  The  Austin 
formation  appears  to  lie  at  about  1896  feet.  If  this  is  true  the 
Del  Rio  may  be  expected  at  about  2350,  or  something  like  the 
actual  level  of  1850  feet  below  sea. 

15  6.  Perrinot  well,  about  2 miles  southwest  of  Martinez,  east 

of  the  Foster  Cross-road  on  J.  F.  Schlather’s  property.  Test  well 

for  oil. 

Soil  0-  2 

Yellow  clay  2-  22 

Shale  22-  63 

Rock  63-  64 

Shale  and  boulders 64-  87 

Shale  87-  150 

Gumbo  150-  236 

Shale  236-  249 

Gumbo  249-  269 

Rock  i. 269-  270 

Shale  270-  297 

Gumbo  297-  307 

Shale  and  boulders 307-  359 

Gumbo  359-  371 

Shale  371-  391 

Gumbo  391-  401 

Shale  401-  438 

Gumbo  438-  446 

Shale  446-  451 

Rock  451-  453 

Shale  453-  478 

Gumbo  478-  483 

Rock  483-  492 

Shale  492-  501 

Gumbo  501-  522 


184  University  of  Texas  Bulletin 

Rock  522-  523 

Shale,  oil  showing 523-  534 

Gumbo  534-  547 

Rock  547-  549 

Gumbo  549-  559 

Rock  559-  565 

Blue  clay  565-  570 

Gumbo  570-  583 

Rock 583-  585 

Gumbo  585-  602 

Sand  and  shale  602-  607 

Gumbo  607-  661 

Rock  661-  663 

Shale,  oil  showing  663-  669 

Gumbo  669-  684 

Shale  and  boulders 684-  709 

Shale  and  gumbo  709-  730 

Gumbo,  very  tough 730-  7 61 

Shale  761-  774 

Gumbo  774-  779 

Shale  and  boulders 77  9-  789 

Soft  rock  % 789-  806 

Shale  806-  816 

Rock  816-  827 

Gumbo  827-  837 

Rock  837-  848 

Shale  848-  860 

Black  sand  and  shale,  showing  oil  and  gas 860-  868 

Gumbo  868-  873 

Black  sand  and  shale 873-  900 

Rock  900-  902 

Not  recorded 902-  953 

Gumbo  953-  984 

Shale  984-  986 

Gumbo  . . 986-10  64 

Chalk  1064-1080 

Shale  1080-1107 

Gumbo  1107-1118 

Shale  1118-1129 

Gumbo  1129-1134 

Shale  1134-1150 

Rock  and  shale .1150-1162 

Shale  1162-1167 

Gumbo  1167-1178 

Shale  1178-1188 

Gumbo  1188-1193 

Shale  1193-1208 


Geology  and  Mineral  Resources  of  Bexar  County  185 


Rock  1208-1212 

Shale,  show  gas  and  oil . . .1212-1239 

Chalk  rock  1239-1375 


This  well  starts  in  the  Tertiary,  probably  in  the  Midway  forma- 
tion, and  extends  into  but  not  through  the  Austin  formation.  The 
dividing  line  between  the  Tertiary  and  Cretaceous  can  scarcely  be 
determined  from  the  log,  although  the  Midway  may  provisionally 
be  regarded  as  extending  to  360  feet,  as  this  is  the  last  record  of 
boulders  suggestive  of  those  of  the  Tertiary  formations.  From 
360  to  something  more  than  1200  feet  is  apparently  referable  to 
the  Navarro  and  Taylor  formations.  Below  about  1239  feet,  the 
drilling  record  indicates  the  Austin  formation  in  which  the  well 
terminates.  Assuming  that  the  top  of  the  Austin  formation  lies  at 
about  1250  feet,  the  Del  Rio  at  this  locality  is  to  be  expected  at 
about  1700  feet  below  the  surface  or  at  about  the  actual  level  of 
1000  feet  below  sea. 

157.  Porch  well,  east  of  the  Pleasanton  Road  between  ;Mit- 
chell’s  Lake  and  the  Medina  River  on  Arroyo  Hondo.  Depth,  1505 
feet;  elevation  about  530  feet.  Test  well  for  oil;  showings  of  oil 
at  about  1000  feet,  and  from  about  1292  to  1493  feet.  No  water 
except  small  amounts  between  60  and  70  feet,  and  a little  salt  water 
at  the  bottom  of  the  hole.  Record  submitted  to  Bureau  of  Eco- 


nomic Geology  by  E.  L.  Porch. 

Soil  and  clay  0-  30 

Hard  pan  30-  5 0 

Soft  sand  rock  50-  6 0 

Gravel,  loose;  water 60-  66 

Very  hard  rock 66-  69 

Sand  fine,  black  69-  72 

Clay,  10"  casing  set  at  81' 72-  87 

Lignite  87-  90 

Sand  rock  90-  13  5 

Very  hard  sand  rock,  gray 135-  137 

Sand  rock  137-  164 

High  grade  lignite  or  coal 164-  172 

Sand  rock  172-  182 

Hard  rock  182-184 

Shale  184-  193 

Hard  sand  rock,  blue 193-  203 

Shale  203-  213 

Gumbo  213-  286 

Shale  and  boulder  286-  297 

Rock,  hard  297-  299 

Gumbo,  very  stiff  29  9-  309 

Rock,  very  hard  309-  312 

Gumbo  312-  333 


186  University  of  Texas  Bulletin 

Sand  rock,  soft 333-  353 

Hard  blue  rock  35  3-  35.5 

, Gumbo  355-  3 62 

Hard  rock  362-  364 

Gumibo  36  4^  379 

Boulder,  flint  379-  381 

Gumbo  381-  3-87 

Rock,  hard  387-  389 

Gumbo,  tough  389-  409 

Rock  409-  410 

Gumbo  410-  417 

Rock  417-  420 

Gumbo  ' 420-  454 

Hard  rock  454-  456 

Gumbo  456-  473 

Rock  473-  474 

Gumbo,  very  stiff  474-  492 

Boulder  . 492-  494 

Gumbo  494-  518 

Gumbo  and  shell 518-  523 

Very  hard  rock 523-  526 

Gumbo  526-  544 

Shale  and  boulder  544-  565 

Gumbo  with  boulder  565-  595 

Gumbo  and  shell  (Cretaceous)  595-  609 

Shale  with  boulders  609-  627 

Rock  627-  629 

Gumbo  629-  637 

Shale  637-  647 

Gumbo  and  boulder  647-  671 

Shale  and  boulder  671-  689 

Gumbo  689-  705 

Rock  705-  706 

Shale  and  shell  706-  719 

Gumbo  719-  775 

Shale  and  shell 775-  791 

Gumbo  791-  865 

Shale  *. 865-  872 

Rock 872-  874 

Shale,  blue 874-  881 

Gumbo  881-  888 

Shale  888-  892 

Gumbo,  light  colored  892-  894 

Shale,  coarse,  blue  894-  897 

Rock,  soft  897-  898 

Shale  and  boulder  898-  904 

Gumbo  904-  966 


Geology  and  Mineral  Resources  of  Bexar  County  187 


Shale,  some  soft 9 66-  9 85 

Shale  and  sand 985-1003 

Gumbo  1003-1056 

Shell  and  rock  1056-1058 

Gumbo  1058-1129 

Shale  and  sand,  compact 1129-1133 

Shale  1133-1138 

Shale,  with  large  proportion  of  green  sand 1138-1148 

Shale  and  darker  sand 1148-1157 

Gumbo,  dark  sand,  very  fine 1157-1171 

Boulder  1171-1172 

Shale  1172-1175 

Gumbo  1175-1180 

Boulder  1180-1181 

Gumbo  1181-1192 

Boulder  or  rock  1192-1193 

Gumbo  1193-1208 

Very  fine  shale  1208-1213 

Gumbo  with  pyrites  1213-1233 

Gumbo,  tough  blue 1233-1292 

Shale,  gas  and  oil  showing 1292-1296 

Soft  shale  and  sand,  gas 1296-1329 

Shale  or  gumbo  and  sand 1329-1394 

Gumbo,  blue,  no  sand 1394-1430 

Shale  and  sand,  gas  and  oil 1430-1464 

Oil  sand,  little  shale 1464-1483 

Very  dark  shale,  sand  1483-1493 

Dark  blue  gumbo  and  sand,  very  hard 1493-1505 


Supplementary  data  from  owners  of  well:  “From  1296  to  1394 

the  shale  or  gumbo  was  in  alternate  layers  of  about  six  inches,  sand 
between;  drilling  was  hard,  while  in  the  shale  or  gumbo  and  would 
go  quickly  through  the  sand.  From  each  sand  layeT  fine  showings 
of  gas  and  some  oil  were  noticed.  Five  joints  of  Layne  & Bowler 
screen  were  set  to  catch  this,  but  was  too  coarse.  A fine  black 
sand  came  through  and  formed  a bridge  and  would  form  as  fast  as 
was  washed  out.  The  oil  sand  from  1464  to  1483  would  undoubt- 
edly have  made  a well  if  same  had  been  properly  cased  and  washed. 
Live  oil  of  light  gravity  and  parafine  base  came  out  continually 
while  going  through  with  heavy  gas  pressure  pieces  of  parafine  as 
large  as  end  of  thumb  came  up  with  cuttings.  In  this  well  there  was 
no  evidence  of  Austin  chalk  which  was  struck  in  other  wells  3 miles 
to  the  northwest  at  1100  to  1200  feet;  other  sections  show  shallow 
oil  ahd  gas,  none  noticed  in  this  well  until  about  1000  feet  down; 
no  water  encountered  except  between  60  and  70  feet,  although  a 
little  salt  water  showed  up  from  the  bottom  of  the  hole.” 


188 


University  of  Texas  Bulletin 


158.  Log  of  Oil  Prospecting  Well  of  W.  C.  Steubing,  2 miles 
southeast  of  Somerset,  Bexar  County,  Texas.  Sarah  Smith  No.  1. 

(Prepared  by  L.  W.  Stephenson  from  samples  furnished  by  the 
owner;  fossils  identified  by  C.  W.  Cooks). 

Thickness  Depth 
feet  feet 

1.  Reddish  brown,  slightly  ferruginous,  fine  sand.  . 4 4 


2.  Light  gray,  very  fine  argillaceous,  micaceous 

sand  blotched  with  yellow  16  20 

3.  Fine  gray  sand  like  No.  2 but  more  completely 

blotched  with  sulphur  yellow  and  some  pur- 
plish tint  20  40 

4.  Dark  gray  finely  sandy,  micaceous,  carbona- 

ceous clay  with  fragments  of  fine  reddish  to 

yellowish  ferruginous  sandstone  20  60 

5.  Gray  fine  slightly  calcareous  sand  with  some 

mica  and  numerous  reddish,  yellowish  and 

brownish  grains;  water  bearing  20  80 

6.  Gray  sand  like  the  preceding,  but  contains 

numerous  small,  white  flaky  grains  that  are 
probably  rotten  shell  fragments,  as  they 
effervesce  freely  in  acid;  water  bearing 20  100 

7.  Fine  gray  clean  sand  with  pinkish  and  yellow- 

ish grains,  and  some  mica;  water  bearing.  ...  20  120 

8.  Dark  gray  fine  micaceous  sand  with  numerous 

fragments  of  gray  shaly  clay 20  140 

9.  Fint  gray  calcareous  sand  with  some  mica  and 

numerous  dark  grains;  water  bearing 20  160 

10.  Gray  sand  like  No.  9;  water  bearing 20  180 

11.  Fine  gray  clean  sand,  with  some  mica  and 

numerous  dark  grains;  water  bearing 20  200 

12.  Gray  sand  like  No.  11,  but  contains  small 

fragments  of  gray  shaly  clay  and  small" frag- 
ments of  vein  calcite;  water  bearing 20  220 

13.  Fine  clean  sand  like  No.  11,  with  a few  frag- 

ments of  shaly  clay;  water  bearing 35  255 

14.  Ground-up  gray  hard  slightly  calcareous  sand- 

stone   4 259 

15.  Fine  gray  clean  sand  with  some  mica  and  nu- 

merous dark  grains 20  279 

16.  Gray  sand  like  No.  15  12  291 

17.  Ground-up  light  gray  medium  grained  sand- 

stone   21  312 

18.  Sandstone  like  No.  17  10  322 

?9.  Fine  gray  sand  with  some  mica,  numerous 

dark  grains,  numerous  fragments  of  gray 


Geology  and  Mineral  Resources  of  Bexar  County  189 


Thickness  Depth 
feet  feet 

shaly  clay,  and  small  particles  of  black 

lignite  22  344 

20.  Light  gray  clean  sand  with  numerous  dark 

grains  and  small  fragments  of  black  lignite.  . 31  375 

21.  Dark  gray  argillaceous  sand  with  some  mica 

and  some  fragments  of  gray  shaly  clay 22  397 

22.  Dark  gray  to  blackish,  finely  sandy  carbona- 

ceous clay,  containing  some  marcasite 16  413 

23.  Dark  gray  carbonaceous  clay  mixed  with  fine 

gray  sand  24  437 

24.  Mottled  mixture  of  fine  white  and  light  gray 

partly  indurated  sand,  the  cementing  sub- 
stance apparently  being  white  and  gray  clay; 
some  fragments  of  gray  shaly  clay  21  458 

25.  Mixture  of  fragments  of  dark  gray  shaly  clay, 

and  white  sandy  clay  (?)  20  478 

26.  Mixture  of  dark  gray  calcareous  sand,  frag- 

ments of  dark  gray  shaly  clay,  and  black 

lignite  20  498 

27.  Mixture  like  No.  26  21  519 

28.  Mostly  fragments  of  gray  shaly  clay,  with 

some  loose  fine  gray  sand,  and  a few  shell 

fragments  19  538 

29.  Mixture  of  fine  gray  calcareous  sand  and  frag- 

ments of  gray  shaly  clay 19  557 

30.  Mixture  like  No.  29;  some  shell  fragments....  21  578 

31.  Mixture  like  No.  30  22  600 

32.  Mixture  like  No.  30;  some  lignite  and  shell 

fragments  21  621 

33.  Mixture  like  No.  30;  recognized  the  fossil 

shell  Toinostoma?  sp — 17  638 

34.  Mixture  like  No.  30;  some  shell  fragments 

and  some  marcasite 21  659 

35.  Mostly  gray  shaly  clay  with  a few  shell  frag- 

ments; recognized  the  fossil  shell  Ringicula 

dalli  Clark?  21  680 

36.  Shaly  clay  like  No.  35;  recognized  the  fossil 

shells  Cyclichna  sp.,  Corbula  sp.,  and  Tur- 

ritella  sp 20  700 

37.  Dark  gray  clay  (gumbo  of  the  driller)  with  a 

few  shell  fragments;  recognized  the  fossil 

shell  Fuses  sp.  cf  F Meleri  Aldrich 21  721 

38.  Gray  shaly  clay  19  740 

39.  Gray  shaly  clay,  with  some  shell  fragments 

recognized  Turritella  sp 21  761 


190 


University  of  Texas  Bulletin 


Thickness  Depth 
feet  feet 


40.  Gray  shaly  clay;  recognized  the  fossil  shells, 
Olivella  mediavia  Harris,  Natica  sp.  Turri- 


tella  sp 

21 

782 

41. 

Gray  shaly  clay,  larger  fragments;  recognized 

the  fossil  shell  Pleions  rugata  (Hilprin)  ? ? . . 

19 

801 

42. 

Dark  gray  clay  (from  bit?) 

21 

822 

43. 

Gray  finely  shaly  clay  

21 

843 

44. 

Gray  shaly  clay;  recognized  the  fossil  shells 

Venericardia,  sp  and  Natica  sp 

22 

865 

45. 

Gray  shaly  clay;  larger  fragments 

20 

885 

46. 

Gray  (finely  shaly  clay  with  a mixture  of  dark 

glauconitic  sand;  recognized  the  fossil  shells 

Venericardia  sp.,  and  Turritella  sp 

21 

906 

47. 

Gray  shaly  clay  and  glauconitic  sand,  like 

No.  4 6 . 

20 

926 

48. 

Gray  shaly  clay  and  glauconitic  sand  like 

No.  46  

21 

947 

49. 

Gray  finely  shaly  clay  

21 

968 

50. 

Gray  finely  shaly  clay  with  some  dark  glau- 

conitic grains  and  some  shell  fragments.  . . . 

21 

989 

51. 

Gray  shaly  clay,  slight  showing  of  oil  and  gas.  . 

23 

1012 

52. 

Gray  shaly  clay  with  some  glauconite  grains; 

recognized  the  fossil  shell  Venericardia  plan- 

icosta  Lamark.  Some  showing  of  oil  and  gas.  . 

21 

1033 

53. 

Shaly  clay  like  No.  52,  slight  showing  of  oil 

and  gas  

22 

1055 

54. 

Shaly  clay  like  No.  52,  gas  and  oil  showing 

increase  

4 

1059 

According  to  Dr.  Cooke,  the  fossils  enumerated  in  the  log  indi- 
cate the  Midway  Age  of  the  containing  beds. 

Continuation  of  Log  of  Oil  Prospecting  Well  .of  W.  C.  Steubing 
(Sarah  Smith  No.  1)  2 miles  southeast  of  Somerset,  Bexar  County, 
Texas.  (Prepared  by  L.  W.  Stephenson  from  samples  furnished  by 
the  owner). 

55.  Light  gray  to  whitish,  highly  calcareous  clay 

or  argillaceous  limestone  ground  to  fine  mud, 
with  fragments  of  platy  impure  limestone.  . 

56.  Gray,  calcareous  somewhat  shaly  clay  with 

some  admixture  of  material  like  No.  55 

57.  Gray,  calcareous,  shaly  clay  

58.  Gray,  shaly  clay  like  No.  57;  observed  2 speci- 

mens of  Foraminifera 

59.  Gray,  shaly  clay,  like  the  preceding,  with  a few 

shell  fragments  


16 

1075 

20 

1095 

20 

1115 

21 

1136 

21 

1157 

Geology  and  Mineral  Resources  of  Bexar  County  191 


Thickness  Depth 


60. 

Gray  shaly  clay  like  the  preceding,  with  a few 

feet 

feet 

shell  fragments,  recognized  Venericardia? 
and  a small  smooth  gastropod 

20 

1177 

61. 

Gray  finely  shaly,  calcareous  clay  

20 

1197 

62. 

Gray  calcareous  clay  like  No.  61  

21 

1218 

62. 

Gray  calcareous  clay  like  No.  61  

21 

1239 

63. 

Gray  calcareous  clay  like  No.  61  

21 

1239 

64. 

Gray  calcareous  clay  like  No.  61  

20 

1259 

65. 

Gray  calcareous  clay  like  No.  61  

20 

1279 

66. 

Gray  calcareous  clay  like  No.  61  

20 

1299 

67. 

Grav  calcareous  clay  like  No.  61  

20 

1319 

68. 

Gray  calcareous  clay  like  No.  61  

20 

1339 

Not  represented  by  sample 

11 

1350 

69. 

Gray  shaly  calcareous  clay  

50 

1400 

70. 

Gray  shaly  calcareous  clay  

20 

1420 

71. 

Gray  shaly  calcareous  clay  

14 

1434 

72. 

Gray  shaly  calcareous  clay  

6 

1440 

73. 

Gray  shaly  calcareous  clay  with  a little  fine  sand 

4 

14  4 4 

74. 

Gray  shaly  clay  like  No.  73  

11 

1455 

75. 

Gray  shaly  clay  like  No.  7 3 

5 

1460 

76. 

Gray  shaly  clay  like  No.  73  

20 

1480 

77. 

Gray  shaly  clay  like  No.  73  

4 

1484 

78. 

Gray  shaly  clay  like  No.  73  

5 

1489 

Not  represented  by  sample 

5 

1494 

79. 

Gray  shaly  clay  like  No.  73  

5 

1499 

80. 

Gray  shaly  clay  like  No.  73;  contains  a small 
gastropod  

4 

1503 

81. 

Gray  shaly  clay  like  No.  73  

21 

1524 

82. 

Gray  shaly  calcareous  clay  and  very  fine  sand . . 

20 

1544 

83. 

Gray  shaly  calcareous  clay  with  some  fine 
sand;  one  or  two  shell  fragments 

21 

1565 

84. 

Gray  shaly  clay  and  some  sand;  like  No.  83.  . . 

21 

1586 

85. 

Gray  shaly  calcareous  clay  and  very  fine  sand.  . 

19 

1605 

86. 

Gray  shaly  calcareous  clay  and  very  fine  sand . . 

21 

1626 

87. 

Gray  shaly  calcareous  clay  and  very  fine  sand.  . 

20 

1646 

88. 

Gray  shaly  calcareous  clay  and  very  fine  sand.  . 

21 

1667 

This  set  of  samples  (Nos.  55-88)  is  very  much  alike  throughout. 
A fragment  of  a Venericardia?  from  sample  No.  60  (depth  1157- 
1177  ft.)  seems  to  indicate  that  the  shalv  clay  at  that  depth  be- 
longs to  the  Midway  group  of  the  Eocene.  Nothing  was  found 
below  that  depth  to  indicate  that  the  well  had  passed  from  the 
Eocene  into  the  underlying  Cretaceous.  If  it  is  all  Eocene  the  strata 
of  this  age  are  thicker  at  this  place  than  we  had  supposed. 


192 


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196  University  of  Texas  Bulletin 

159.  Walsch  Oil  Company,  well  No.  1 on  south,  side  of  Leon 
Creek  in  Mission  Oil  Field,  near  the  Applewhite  Road  crossing. 
This  well  starts  probably  in  the  Navarro  formation,  as  indicated 
by  the  greensand  horizon  near  the  surface.  They  probably  termi- 
nate in  the  Austin  formation  and  illustrate  the  character  of  drilling 


in  the  Mission  oil  field. 

Gravel  0-  18 

Greensand  and  soapstone L8-  40 

Clay,  blue  40-  60 

Clay  and  gumbo  60-  80 

Shale  and  rock,  soft;  a little  gas 80-  97 

Shale,  a little  oil . 97-  180 

Rock  130-  132 

Shale  132-  134 

Rock  134-  135 

Shale  135-  140 

Rock  and  sand  140-  155 

Shale  155-  167 

Rock  167-  181 

Mud  and  small  boulders  181-  192 

Shale  192-  250 

Shale  and  mud  250-  350 

Rock  350-  352 

Gumbo  352-  360 

Rock  360-  364 

Gumbo  and  shale  364-  430 

Rock  430-  432 

Shale  432-  441 

Rock,  hard  and  soft 441-  445 

Shale  and  mud  445-  523 

Rock 523-  530 

Shale  530-  637 

Rock 637-  657 

Shale  657-  661 

Rock  661-  665 

Shale  665-  670 

Gypsum  670-  698 

Rock  698-  702 

Shale  702-  765 

Rock  765-  786 

Shale  786-  791 

Rock 791-  801 

Shale  801-  814 

Iron  pyrite  814-  815 

Shale  815-  821 

Boulders  821-  824 


Geology  and  Mineral  Resources  of  Bexar  County  197 


Shale  824-  835 

Rock  835-  853 

Shale  853-  861 

Rock  861-  869 

Rock  869-  876 

Shale  and  pyrite 876-  893 

Pyrites,  hard 893-  902 

Shale  . . . . 902-  925 

Rock 925-  937 

Rock  and  shale 937-  957 

Shale  957-  982 

Rock,  hard  982-  988 

Rock  and  shale  . 988-1002 

Brown  rock  1002-1024 

Shale  and  some  iron  pyrite . 1024-1067 


160.  Wolfe  and  Elder,  Alta  Vista  Oil  Field,  depth  1286,  Eleva- 
tion 600.  Test  well  for  oil. 

Samples  from  this  well  from  965  feet  to  the  bottom  were  sub- 
mitted by  E.  L.  Porch  and  described  by  Dr.  J.  A.  Udden  (Mns). 
According  to  Dr.  Udden’s  interpretation  of  the  samples  the  well 
entered  the  Buda  limestone  at  1270  feet  and  terminated  in  this 
formation  at  1286  feet.  From  this  record  it  would  seem  that  the 
Del  Rio  formation  is  to  be  expected  at  this  locality  at  between 
1300  and  1400  feet,  or  at  an  actual  elevation  of  between  700  and  800 
feet  below  sea  level. 


INDEX 


Page 

Ackermaft,  H.  J.,  well  of....  143 


Alamo  8 

Alamo  Heights  42 

Alamo  Portland  cement. ....  .108 

Alamo  Waterworks  well  143 

Alectryonia  larva  50 

Allen,  D.  J.,  well  of  143 

Alluvial  deposits  72 

Alta  Vista  oil  field  121,  122 

Alta  Vista  structure  85 

Area  of  artesian  flow  101 

Artesian  water  97 

Artesian  wells  98 

Austin  chalk,  analysis  of 109 

Austin  formation  108,  116 

oil  from  122,  124 

water  of  104 

Austin  Hills  16 

Aviation  Post,  well  at  37 

Avicula  43 

Babcock  Road  96 

Baculites  43 

Baker,  C.  L.  8,  43,  ,52,  55,  58, 

112,  115 

Balcones  escarpment  ..11,  13,  77 

Bandera  Road  95 

Barbattia  sp 43 

Basement  sands  21 

Basse,  Ed.  E.,  well  of 143 

Beckman  26 

Bern  Brick  Co 112 

Bend  formation  19 

Benke,  Kate,  well  of  .........  144 

Bentonite  115 

Berry,  E.  W 10 

Bexar  County,  area  of  7 

drainage  12 

literature  on  10 

settlements  in  7 

topography  12 

Biering,  H.  T.,  w'ell  of 144 

Blanco  Road  90 

Blank,  J.  T.,  well  of  144 

Bluewing  Club,  well  of  145 

Boerman,  D.,  well  of  147 

Bose,  Emil  10,  40 

Brackenridge  Coal  Company..  119 
Brackenridge  Park  ..42,  81,  109 

Brendle,  H.,  well  of  147 

Brooks  Field  8 

Buda  formation  ....31,  110,  116 
water  of  103 


Buda  limestone,  analysis  of...  110 


Page 

Building  brick  112 

Building  stone  121 

Bulimulus  73,  74 

Bulverde  Road  91 

Calcareous  concretions  75 

Caliche  75 

Camp  Bullis  Reservation  ....  19 

log  of  well  on .131 

Camp  John  Wise  8 

Camp  Stanley  8 

Carbon  dioxide  in  under- 
ground water 107 

Carrizo  formation  63 

Carrizo  sand  hills  18 

Castroville  Road  114,  117 

Cave  deposits 73 

Cement 108 

Cenozoic  54 

Clamp,  C.  C.,  well  of  147 

Clay  112 

Climate  13 

Cohen  and  Roby,  well  of  ....171 

Collins’  Gardens,  well  at  ....148 

Collins  Mfg.  Co.,  well  of  148 

Columnar  section  20 

Comanchean  21 

Comanche  Peak  formation  ...  24 

Conception  Mission  7 

Concrete  116 

Concretions  58 

Cooke,  C.  W 190 

Cretaceous  21 

Crosby  lease,  wells  on  125 

Crosby  well  No.  4 172 

Culebra  Road 95 

Culebra  structure  83 

Cyprina  mediale  24 

Del  Rio  clay  110 

Del  Rio  formation  28,  86,  87,  112 

water  of  103 

Del  Rio  Plain  16 

Dentalium  112 

Deussen,  Alexander  9,  22,  75,  129 

Dickinson  well  148 

Dips  43,  51,  58,  85,  113 

Dumble,  E.  T 10 

Eagleford  formation  34,  111,  116 

water  of  104 

Earle  62 

Economic  Geology  97 

Edwards  flint  hills  15 


Edwards  formation..  25,  110, 
116,  120 


200 


University  "of  Texas  Bulletin 


Page 

water  of  101 

Edwards  limestone,  analysis 

of  120 

Elephas  ^ . 73 

Elevations  12 

Eocene  54 

Exogyra  arietina 28,  29 

costata  50,  94,  115 

laeviuscula 40,  43 

ponderosa 40,  41,  45,  47,  48 

texana  25 

Faulting  29 

Faults  77 

Flood-plain  deposits 64 

Flowing  artesian  wells  102 

Fort  Sam  Houston  8 

well  at  22,  81 

Fredericksburg  Road  96 

Friesenhahn,  A.,  cav^of.  ...  73 

Frio  Road  93 

Fuller’s  earth  114 

Gartner,  T.  A 22 

Gas  . . . . 121 

Gas  Ridge  field  7. .’.7.7.7 .122,’  123 

Geological  map  86 

Georgetown  formation  27,  110,  116 

water  of  101 

Geunther  Milling  Co.,  well  of.  149 

Glauconite  49,  52,  117 

Glenrose  formation 23,  116 

water  of  100 

Glenrose  Hills  14 

Goforth,  A.  E.,  well  of 38,  149 

Government  well  at  Aviation 

Post  149 

at  Ft.  Sam  Houston  150 

Green  marl  49 

Greensand,  analysis  of, 117 

Grote,  F.,  well  of .’ 151 

Gryphea  aucella 40 

micronata  29 

vesicularis  50 

Gulf  Coastal  Plains  10 

Hamilton,  H.  L 54 

Harrison,  Judd,  well  of 151 

Harrison  property,  wells  on..  125 

Hayes,  C.  W 75 

Herff  well  151 

Hickory  formation  19 

Hill  25 

Hill  & Roby,  well  of  132 

Hill,  R.  T 10,  21,  50,  77 

Hoffman  Ranch,  exposures  on.  33 

Hofheintz,  R.  H.,  well  of  152 

Holtz  well  152 

Hot  Well  Hotel,  well  at 153 


Hydrogen  sulphide  in  under- 


ground waters  106 

Index  to  map  entries  87 

Ingram  well  173 

Kearney  Oil  & Pipe  Line  Co., 


Kelly  Field  8 

Kelly  Field  Plain  70 

Kimbly-Brown  wells  173 

Kurz,  C.,  wells  of 125 

Lakeview  addition,  well  in...  155 

Lamb,  J.  K.,  well  of  49,  174 

Legler,  W.  F.,  well  of  156 

Leona  formation  69 

Leon  Creek,  exposures  on. 51,  117 
Leon  Springs,  Military 

Reservation  8 

log  of  well  on  129 

wells  on  19 

Lignite  H8 

Lime  120 

Limestone  119 

Liopsitha  elegantula  43 

Locke,  J.,  well  of  156 

Lorenz,  Alex,  well  of 156 

Lunatia  pedernalis  24 

Madison,  R.  M 9 

Map  86 

Mars  Discovery  well  176 

Masterson,  B.  F.,  well  of 156 

Mathey  well  45,  54,  178 

Maty  ear,  Chas.,  well  of  157 

Medina  Fuller’s  Earth  Co 114 

well  of  157 

Medina  Oil  Co.,  well  of  157 

Medina  River,  alluvial  de- 
posits of  72 

exposures  on  58,  62 

Mercke,  R.,  well  of  21 

Mesozoic  21 

Midway  formation  54,  116 

Midway-Wilcox  Hills  18 

Mission  Oil  Field 121,  123 

Missions  7 

Monopleura  27 

Mt.  Selman  formation  64 

Nacogdoches  Road  91 

National  Oil  Co.,  well  of  180 

Navarro  formation  ..49,  112, 

114,  117 

oil  from  122 

water  of  104 

Non-flowing  artesian  wells....  102 

Oil  121 

Oliver  well  180 


Geology  and  Mineral  Resources  of  Bexar  County  201 


Page 

Openheimer  well  180 

Packsaddle  schists  21 

Pancoast,  A.  C 9 

Park  Oil  & Gas  Co.,  well  of  ..180 

Pearsall  Road  93,  117 

Pecten  43 

Perrinot  well  > 183 

Petroleum  121 

Phillips,  W.  B.  ...10,  108,  117 

Phosphate  49 

Phosphatic  pebbles,  analysis  of  118 

Physiography 14 

Placenticeras  sp 43 

Pleasanton  Road  92 

Pleistocene  64 

Porch,  E.  L.  : 123 

Porch  well  185 

Potash  49 

Potassium  117 

Potranca  Road  94 

Pre-Cretaceous  19 

Pyrite,  source  of  hydrogen 

sulphide  108 

Radiolites  27 

Rainfall  13 

Recent  74 

Red  Lands  16,  25 

Requienia  27 

Ridder,  A.  J.,  well  of  . .22,  49,  139 
Road  materials  128 

Sabre-toothed  tiger  74 

Saint  Denis  7 

Saint  Hedwig  Road  92 

Saint  Louis  College,  well  at  ..160 

Salado  Creek  32,  96 

Salado  Creek,  section  on  ....  46 

Salado  River,  springs  of  105 

Salado  Waterworks,  well  at  . . 160 
San  Antonio  and  Aransas 

Pass  Ry.,  well  of  161 

San  Antonio  City  Water 

Supply,  well  of  161,  162 

San  Antonio  city  well  162 

San  Antonio  de  Valero, 

mission  of  7 

San  Antonio  Lime  Co 27,  120 

San  Antonio  Portland 

Cement  Co 108 

well  of  162 

San  Antonio  River  76 

springs  of  105 

San  Antonio  Sewer  Pipe 

Works  112 

San  Antonio  structure  84 

San  Pedro  Park  40,  42,  105 

Saunders  Creek,  exposures  ...  58 
Sauer,  George,  well  of  163 


Page 


Scaphites  sp 43 

Schists  19 

Shattuck  well  163 

Shumard,  Geo.  C 10 

Shiwneier,  Henry,  well  of  ....163 
Smith,  Sarah,  well  of  ....55,  187 

Somerset  oil  field  121,  124 

Somerset  Road  92 

Southern  Ice  Co.,  well  of 164 

South  Medina  Oil  field  125 

Southwest  Land  Corporation 

well  of  164 

Source  of  hydrogen  sulphide.  .106 

Springs  104 

Star  Clay  Products  Co 112 

Stephenson,  L.  W.  9,  43,  45, 

i .56,  62,  188 

Steubing,  W.  C.,  well  of  . . 187 

Steve’s  Irrigated  Gardens, 

well  at  164 

Steve’s  well  . . . .* 165 

Stratigraphic  geology  19 

Stream  Terrace  Plains  18 

Structural  geology  77 

Sulphides,  oxidation  of  107 

Sulphur  water  105 

Superior  Oil  Co.,  well  of  165 

Table  of  geologic  formations..  20 

Tabulated  data  on  wells  136 

Tapetate  75 

Taylor  formation  44,  108,  112,  114 
oil  and  gas  from  ....122,  124 

water  of  104 

Taylor-Navarro  Plain  17 

Taylor,  T.  N 10,  105 

Terrell,  J.  H.,  well  of  167 

Terrell  Hot  Wells  167 

Tertiary,  water  of  104 

Tezel,  Louis,  well  of  168 

Topography  12 

Townsite  well  168 

Travis,  W.  B 8 

Travis  Peak  formation  21 

water  of  100 

Trinity  21 

Turritella  112 

Tylostoma  24 

Udden,  J.  A.  9,  19,  22,  45, 

49,  57,  110,  129 

Underground  water  97 

Union  Meat  Co.,  well  of  168 

U.  S.  Geological  Survey 9 

Uvalde  formation  65 


Vaughan,  T.  W.  ..21,  25,  28, 

50,  69,  77 

Venericardia  21,  25,  28 

Villa  de  Bexar,  mission  of 7 


202 


University  of  Texas  Bulletin 


Pago 

Vogt,  Win.,  well  of  168 

Voight,  A.,  well  of  169 

Volutilithes  112 

Van  Ormy 58 

Walsch  Oil  Co.,  well  of  196 

Warm  sulphur  water  ; .105 

Waring  Estate,  well  on 22, 

38,  100,  169 

Well  records  129 


Page 

Wells  entering  the  Pre- 

Cretaceous  formations  129 

Wells  terminating  in  the 

Comanchean  formations  ...135 
in  the  Upper  Cretaceous  ...171 
Wilcox  formation  ....  57,  112,  116 

lignite  of  118,  167 

Wolfe  and  Elder,  well  of 197 


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UNIVERSITY  OF  TEXAS 

BUREAU  OF  ECONOMIC  GEOLOGY  AND-  TECHNOLOGY 
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BULLETIN  1932. 


GEOLOGICAL  MAP  OF  BEXAR  COUNTY,  TEXAS 

BY  E.  H.  SELLAKDS 


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